Method for reporting channel status information in wireless communication system supporting change in use of wireless resources, and device therefor

ABSTRACT

The present invention relates to a method and a device for reporting channel status information of a terminal in a wireless communication system supporting a change in use of wireless resources. Particularly, the method comprises the steps of: receiving a change-in-use message for a dynamic change of wireless resource use; measuring channel status information in a channel status information (CSI) reference resource section corresponding to the change-in-use message; and reporting the channel status information to a base station, wherein the CSI reference resource section has a first CSI measurement resource set and a second CSI measurement resource set, the first CSI measurement resource set has a plurality of first wireless resources configured to allow the use of wireless resources to be fixed, and the second CSI measurement resource set has a plurality of second wireless resources configured to allow the use of wireless resources to be reset.

TECHNICAL FIELD

The present invention relates to a wireless communication system and,more particularly, to a method of reporting channel state information ina wireless communication system supporting usage change of a radioresource and an apparatus therefor.

BACKGROUND ART

A 3rd generation partnership project long term evolution (3GPP LTE)(hereinafter, referred to as 1TE′) communication system which is anexample of a wireless communication system to which the presentinvention can be applied will be described in brief

FIG. 1 is a diagram illustrating a network structure of an EvolvedUniversal Mobile Telecommunications System (E-UMTS) which is an exampleof a wireless communication system. The E-UMTS is an evolved version ofthe conventional UMTS, and its basic standardization is in progressunder the 3rd Generation Partnership Project (3GPP). The E-UMTS may bereferred to as a Long Term Evolution (LTE) system. Details of thetechnical specifications of the UMTS and E-UMTS may be understood withreference to Release 7 and Release 8 of “3rd Generation PartnershipProject; Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), basestations (eNode B; eNB), and an Access Gateway (AG) which is located atan end of a network (E-UTRAN) and connected to an external network. Thebase stations may simultaneously transmit multiple data streams for abroadcast service, a multicast service and/or a unicast service.

One or more cells exist for one base station. One cell is set to one ofbandwidths of 1.44, 3, 5, 10, 15 and 20 MHz to provide a downlink oruplink transport service to several user equipments. Different cells maybe set to provide different bandwidths. Also, one base station controlsdata transmission and reception for a plurality of user equipments. Thebase station transmits downlink (DL) scheduling information of downlinkdata to the corresponding user equipment to notify the correspondinguser equipment of time and frequency domains to which data will betransmitted and information related to encoding, data size, and hybridautomatic repeat and request (HARQ). Also, the base station transmitsuplink (UL) scheduling information of uplink data to the correspondinguser equipment to notify the corresponding user equipment of time andfrequency domains that can be used by the corresponding user equipment,and information related to encoding, data size, and HARQ. An interfacefor transmitting user traffic or control traffic may be used between thebase stations. A Core Network (CN) may include the AG and a network nodeor the like for user registration of the user equipment. The AG managesmobility of the user equipment on a Tracking Area (TA) basis, whereinone TA includes a plurality of cells.

Although the wireless communication technology developed based on WCDMAhas been evolved into LTE, request and expectation of users andproviders have continued to increase. Also, since another wirelessaccess technology is being continuously developed, new evolution of thewireless communication technology will be required for competitivenessin the future. In this respect, reduction of cost per bit, increase ofavailable service, use of adaptable frequency band, simple structure andopen type interface, proper power consumption of the user equipment,etc. are required.

In order to assist an eNB and efficiently managing a wirelesscommunication system, a UE periodically and/or aperiodically reportsstate information about a current channel to the eNB. The reportedchannel state information may include results calculated inconsideration of various situations, and accordingly a more efficientreporting method is needed.

DISCLOSURE Technical Problem

An object of the present invention based on the above-describeddiscussion is to provide a method of reporting channel state informationin a wireless communication system supporting usage change of a radioresource and an apparatus therefor.

The technical objects that can be achieved through the present inventionare not limited to what has been particularly described hereinabove andother technical objects not described herein will be more clearlyunderstood by persons skilled in the art from the following detaileddescription.

Technical Solution

In an aspect of the present invention for solving the above-describedproblem, provided herein is a method of reporting channel stateinformation (CSI) by a user equipment (UE) in a wireless communicationsystem supporting usage change of a radio resource, including receivinga reconfiguration message for dynamically changing usage of the radioresource, measuring the CSI in a CSI reference resource durationcorresponding to the reconfiguration message, and reporting the CSI to abase station (BS), wherein the CSI reference resource duration includesa first CSI measurement resource set and a second CSI measurementresource set, the first CSI measurement resource set includes aplurality of first radio resources having fixed radio resource usage,and the second CSI measurement resource set includes a plurality ofsecond radio resources having reconfigurable radio resource usage.

The CSI may be set to a predefined value to indicate a fallback modewhen the second CSI measurement resource set is invalid. The CSI may bereported through a predefined uplink resource for the fallback mode.

When the second CSI measurement resource set is invalid, the CSI may beset to CSI reported prior to the CSI reference resource duration, boththe first CSI measurement resource set and the second CSI measurementresource set being valid.

The CSI reference resource duration may be defined such that only radioresources after a subframe in which the reconfiguration message istransmitted are valid.

The CSI reference resource duration may be defined such that only radioresources present after a start subframe of a time window in which thereconfiguration message is transmitted are valid. The time window may bedefined according to a period at which the reconfiguration message isidentically transmitted.

The CSI reference resource duration may be defined such that only radioresources present prior to 4 ms from a subframe for reporting the CSIare valid.

Reporting of the CSI corresponds to aperiodic CSI reporting and the CSIreference resource duration may be defined such that only radioresources present prior to a timing at which a triggering message forreporting the CSI is received are valid.

In another aspect of the present invention for solving theabove-described problem, provided herein is a user equipment (UE) forreporting channel state information (CSI) in a wireless communicationsystem supporting usage change of a radio resource, including a radiofrequency unit and a processor, wherein the processor is configured toreceive a reconfiguration message for dynamically changing usage of theradio resource, measure the CSI in a CSI reference resource durationcorresponding to the reconfiguration message, and report the CSI to abase station (BS), the CSI reference resource duration includes a firstCSI measurement resource set and a second CSI measurement resource set,the first CSI measurement resource set includes a plurality of firstradio resources having fixed radio resource usage, and the second CSImeasurement resource set includes a plurality of second radio resourceshaving reconfigurable radio resource usage.

Advantageous Effects

According to embodiments of the present invention, channel stateinformation reporting can be efficiently performed in a wirelesscommunication system supporting usage change of a radio resource.

The effects that can be achieved through the present invention are notlimited to what has been particularly described hereinabove and otheradvantages not described herein will be more clearly understood bypersons skilled in the art from the following detailed description

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

FIG. 1 is a diagram illustrating a network structure of an EvolvedUniversal Mobile Telecommunications System (E-UMTS) which is an exampleof a wireless communication system.

FIG. 2 is a diagram illustrating structures of a control plane and auser plane of a radio interface protocol between a user equipment andE-UTRAN based on the 3GPP radio access network standard.

FIG. 3 is a diagram illustrating physical channels used in a 3GPP LTEsystem and a general method for transmitting a signal using the physicalchannels.

FIG. 4 is a diagram illustrating a structure of a radio frame used in anLTE system.

FIG. 5 illustrates a resource grid of a DL slot.

FIG. 6 illustrates the structure of a DL subframe.

FIG. 7 is a diagram illustrating an EPDCCH and a PDSCH scheduled by theEPDCCH.

FIG. 8 illustrates the case in which legacy subframes are classifiedinto a static subframe set and a flexible subframe set in a TDD systemenvironment

FIG. 9 is a diagram referred to in explaining ambiguity of CSI reportingand location determination of a CSI reference resource due to failure ofreception of a reconfiguration message by a UE in a legacy wirelesscommunication system.

FIG. 10 is a diagram referred to in explaining an ambiguity problem of aCSI reporting timing of a specific UE (eIMTA UE) and/or atiming/location of a valid reference resource (e.g., CSI referenceresource) linked with corresponding CSI reporting.

FIG. 11 is a diagram referred to in explaining one embodiment of thepresent invention.

FIG. 12 illustrates a BS and a UE that are applicable to an embodimentof the present invention.

BEST MODE

The following technology may be used for various wireless accesstechnologies such as CDMA (code division multiple access), FDMA(frequency division multiple access), TDMA (time division multipleaccess), OFDMA (orthogonal frequency division multiple access), andSC-FDMA (single carrier frequency division multiple access). The CDMAmay be implemented by the radio technology such as UTRA (universalterrestrial radio access) or CDMA2000. The TDMA may be implemented bythe radio technology such as global system for mobile communications(GSM)/general packet radio service (GPRS)/enhanced data rates for GSMevolution (EDGE). The OFDMA may be implemented by the radio technologysuch as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, andevolved UTRA (E-UTRA). The UTRA is a part of a universal mobiletelecommunications system (UMTS). A 3rd generation partnership projectlong term evolution (3GPP LTE) is a part of an evolved UMTS (E-UMTS)that uses E-UTRA, and adopts OFDMA in a downlink and SC-FDMA in anuplink. LTE-advanced (LTE-A) is an evolved version of the 3GPP LTE.

For clarification of the description, although the following embodimentswill be described based on the 3GPP LTE/LTE-A, it is to be understoodthat the technical spirits of the present invention are not limited tothe 3GPP LTE/LTE-A. Also, specific terminologies hereinafter used in theembodiments of the present invention are provided to assistunderstanding of the present invention, and various modifications may bemade in the specific terminologies within the range that they do notdepart from technical spirits of the present invention.

FIG. 2 is a diagram illustrating structures of a control plane and auser plane of a radio interface protocol between a user equipment andE-UTRAN based on the 3GPP radio access network standard. The controlplane means a passageway where control messages are transmitted, whereinthe control messages are used by the user equipment and the network tomanage call. The user plane means a passageway where data generated inan application layer, for example, voice data or Internet packet dataare transmitted.

A physical layer as the first layer provides an information transferservice to an upper layer using a physical channel. The physical layeris connected to a medium access control (MAC) layer via a transportchannel, wherein the medium access control layer is located above thephysical layer. Data are transferred between the medium access controllayer and the physical layer via the transport channel. Data aretransferred between one physical layer of a transmitting side and theother physical layer of a receiving side via the physical channel. Thephysical channel uses time and frequency as radio resources In moredetail, the physical channel is modulated in accordance with anorthogonal frequency division multiple access (OFDMA) scheme in adownlink, and is modulated in accordance with a single carrier frequencydivision multiple access (SC-FDMA) scheme in an uplink.

A medium access control (MAC) layer of the second layer provides aservice to a radio link control (RLC) layer above the MAC layer via alogical channel. The RLC layer of the second layer supports reliabledata transmission. The RLC layer may be implemented as a functionalblock inside the MAC layer. In order to effectively transmit data usingIP packets such as IPv4 or IPv6 within a radio interface having a narrowbandwidth, a packet data convergence protocol (PDCP) layer of the secondlayer performs header compression to reduce the size of unnecessarycontrol information.

A radio resource control (RRC) layer located on the lowest part of thethird layer is defined in the control plane only. The RRC layer isassociated with configuration, re-configuration and release of radiobearers (‘RBs’) to be in charge of controlling the logical, transportand physical channels. In this case, the RB means a service provided bythe second layer for the data transfer between the user equipment andthe network. To this end, the RRC layers of the user equipment and thenetwork exchange RRC message with each other. If the RRC layer of theuser equipment is RRC connected with the RRC layer of the network, theuser equipment is in an RRC connected mode. If not so, the userequipment is in an RRC idle mode. A non-access stratum (NAS) layerlocated above the RRC layer performs functions such as sessionmanagement and mobility management.

One cell constituting a base station eNB is set to one of bandwidths of1.4, 3.5, 5, 10, 15, and 20 MHz and provides a downlink or uplinktransmission service to several user equipments. At this time, differentcells may be set to provide different bandwidths.

As downlink transport channels carrying data from the network to theuser equipment, there are provided a broadcast channel (BCH) carryingsystem information, a paging channel (PCH) carrying paging message, anda downlink shared channel (SCH) carrying user traffic or controlmessages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted via the downlink SCH or anadditional downlink multicast channel (MCH). Meanwhile, as uplinktransport channels carrying data from the user equipment to the network,there are provided a random access channel (RACH) carrying an initialcontrol message and an uplink shared channel (UL-SCH) carrying usertraffic or control message. As logical channels located above thetransport channels and mapped with the transport channels, there areprovided a broadcast control channel (BCCH), a paging control channel(PCCH), a common control channel (CCCH), a multicast control channel(MCCH), and a multicast traffic channel (MTCH).

FIG. 3 is a diagram illustrating physical channels used in a 3GPP LTEsystem and a general method for transmitting a signal using the physicalchannels.

The user equipment performs initial cell search such as synchronizingwith the base station when it newly enters a cell or the power is turnedon at step S301. To this end, the user equipment synchronizes with thebase station by receiving a primary synchronization channel (P-SCH) anda secondary synchronization channel (S-SCH) from the base station, andacquires information such as cell ID, etc. Afterwards, the userequipment may acquire broadcast information within the cell by receivinga physical broadcast channel (PBCH) from the base station. Meanwhile,the user equipment may identify a downlink channel status by receiving adownlink reference signal (DL RS) at the initial cell search step.

The user equipment which has finished the initial cell search mayacquire more detailed system information by receiving a physicaldownlink shared channel (PDSCH) in accordance with a physical downlinkcontrol channel (PDCCH) and information carried in the PDCCH at stepS302.

Afterwards, the user equipment may perform a random access procedure(RACH) such as steps S303 to S306 to complete access to the basestation. To this end, the user equipment may transmit a preamble througha physical random access channel (PRACH) (S303), and may receive aresponse message to the preamble through the PDCCH and the PDSCHcorresponding to the PDCCH (S304). In case of a contention based RACH,the user equipment may perform a contention resolution procedure such astransmission (S305) of additional physical random access channel andreception (S306) of the physical downlink control channel and thephysical downlink shared channel corresponding to the physical downlinkcontrol channel.

The user equipment which has performed the aforementioned steps mayreceive the physical downlink control channel (PDCCH)/physical downlinkshared channel (PDSCH) (S307) and transmit a physical uplink sharedchannel (PUSCH) and a physical uplink control channel (PUCCH) (S308), asa general procedure of transmitting uplink/downlink signals. Controlinformation transmitted from the user equipment to the base station willbe referred to as uplink control information (UCI). The UCI includesHARQ ACK/NACK (Hybrid Automatic Repeat and reQuestAcknowledgement/Negative-ACK), SR (Scheduling Request), CSI (ChannelState Information), etc. In this specification, the HARQ ACK/NACK willbe referred to as HARQ-ACK or ACK/NACK (A/N). The HARQ-ACK includes atleast one of positive ACK (simply, referred to as ACK), negative ACK(NACK), DTX and NACK/DTX. The CSI includes CQI (Channel QualityIndicator), PMI (Precoding Matrix Indicator), RI (Rank Indication), etc.Although the UCI is generally transmitted through the PUCCH, it may betransmitted through the PUSCH if control information and traffic datashould be transmitted at the same time. Also, the user equipment maynon-periodically transmit the UCI through the PUSCH in accordance withrequest/command of the network.

FIG. 4 is a diagram illustrating a structure of a radio frame used in anLTE system.

Referring to FIG. 4, in a cellular OFDM radio packet communicationsystem, uplink/downlink data packet transmission is performed in a unitof subframe, wherein one subframe is defined by a given time intervalthat includes a plurality of OFDM symbols.

The 3GPP LTE standard supports a type 1 radio frame structure applicableto frequency division duplex (FDD) and a type 2 radio frame structureapplicable to time division duplex (TDD).

FIG. 4(a) is a diagram illustrating a structure of a type 1 radio frame.The downlink radio frame includes 10 subframes, each of which includestwo slots in a time domain. A time required to transmit one subframewill be referred to as a transmission time interval (TTI). For example,one subframe may have a length of lms, and one slot may have a length of0.5 ms. One slot includes a plurality of OFDM symbols in a time domainand a plurality of resource blocks (RB) in a frequency domain. Since the3GPP LTE system uses OFDM in a downlink, OFDM symbols represent onesymbol interval. The OFDM symbol may be referred to as SC-FDMA symbol orsymbol interval. The resource block (RB) as a resource allocation unitmay include a plurality of continuous subcarriers in one slot.

The number of OFDM symbols included in one slot may be varied dependingon configuration of a cyclic prefix (CP). Examples of the CP include anextended CP and a normal CP. For example, if the OFDM symbols areconfigured by the normal CP, the number of OFDM symbols included in oneslot may be 7. If the OFDM symbols are configured by the extended CP,since the length of one OFDM symbol is increased, the number of OFDMsymbols included in one slot is smaller than that of OFDM symbols incase of the normal CP. For example, in case of the extended CP, thenumber of OFDM symbols included in one slot may be 6. If a channel stateis unstable like the case where the user equipment moves at high speed,the extended CP may be used to reduce inter-symbol symbol interference.

If the normal CP is used, since one slot includes seven OFDM symbols,one subframe includes 14 OFDM symbols. At this time, first maximum threeOFDM symbols of each subframe may be allocated to a physical downlinkcontrol channel (PDCCH), and the other OFDM symbols may be allocated toa physical downlink shared channel (PDSCH).

FIG. 4(b) is a diagram illustrating a structure of a type 2 radio frame.The type 2 radio frame includes two half frames, each of which includesfour general subframes, which include two slots, and a special subframewhich includes a downlink pilot time slot (DwPTS), a guard period (GP),and an uplink pilot time slot (UpPTS).

In the special subframe, the DwPTS is used for initial cell search,synchronization or channel estimation at the user equipment. The UpPTSis used for channel estimation at the base station and uplinktransmission synchronization of the user equipment. In other words, theDwPTS is used for downlink transmission, whereas the UpPTS is used foruplink transmission. Especially, the UpPTS is used for PRACH preamble orSRS transmission. Also, the guard period is to remove interferenceoccurring in the uplink due to multipath delay of downlink signalsbetween the uplink and the downlink.

Configuration of the special subframe is defined in the current 3GPPstandard document as illustrated in Table 1 below. Table 1 illustratesthe DwPTS and the UpPTS in case of T_(S)=1/(15000×2048), and the otherregion is configured for the guard period.

TABLE 1 Normal cyclic prefix in downlink UpPTS Extended cyclic prefix indownlink Normal Extended UpPTS Special subframe cyclic prefix cyclicprefix Normal cyclic Extended cyclic configuration DwPTS in uplink inuplink DwPTS prefix in uplink prefix in uplink 0  6592 · T_(s) 2192 ·T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760 ·T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600· T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5  6592· T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 ·T_(s) 7 21952 · T_(s) 12800 · T_(s) 8 24144 · T_(s) — — — 9 13168 ·T_(s) — — —

In the meantime, the structure of the type 2 radio frame, that is,uplink/downlink configuration (UL/DL configuration) in the TDD system isas illustrated in Table 2 below.

TABLE 2 Uplink- Downlink- downlink to-Uplink config- Switch-pointSubframe number uration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U UD S U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D DD D D 6 5 ms D S U U U D S U U D

In the above Table 2, D means the downlink subframe, U means the uplinksubframe, and S means the special subframe. Also, Table 2 alsoillustrates a downlink-uplink switching period in the uplink/downlinksubframe configuration of each system.

The structure of the aforementioned radio frame is only exemplary, andvarious modifications may be made in the number of subframes included inthe radio frame, the number of slots included in the subframe, or thenumber of symbols included in the slot.

FIG. 5 illustrates a resource grid of a DL slot.

Referring to FIG. 5, a DL slot includes N_(symb) ^(DL) OFDM symbols inthe time domain and N_(RB) ^(DL) in the frequency domain. Each RBincludes N_(sc) ^(RB) subcarriers and thus the DL slot includes N_(RB)^(DL)×N_(sc) ^(RB) subcarriers in the frequency domain. Although FIG. 5illustrates the case in which a DL slot includes 7 OFDM symbols and anRB includes 12 subcarriers, the present invention is not limitedthereto. For example, the number of OFDM symbols included in the DL slotmay differ according to CP length.

Each element on the resource grid is referred to as a resource element(RE). One RE is indicated by one OFDM symbol index and one subcarrierindex. One RB includes N_(symb) ^(DL)×N_(sc) ^(RB) REs. The number ofRBs, N_(RB) ^(DL), included in a DL slot depends on DL bandwidthconfigured in a cell.

FIG. 6 illustrates the structure of a DL subframe.

Referring to FIG. 6, up to three (or four) OFDM symbols at the start ofthe first slot of a DL subframe are used as a control region to whichcontrol channels are allocated and the other OFDM symbols of the DLsubframe are used as a data region to which a PDSCH is allocated. DLcontrol channels defined for an LTE system include a physical controlformat indicator channel (PCFICH), a physical downlink control channel(PDCCH), and a physical hybrid ARQ indicator channel (PHICH). The PCFICHis transmitted in the first OFDM symbol of a subframe, carryinginformation about the number of OFDM symbols used for transmission ofcontrol channels in the subframe. The PHICH delivers a HARQ ACK/NACKsignal as a response to UL transmission.

Control information carried on the PDCCH is called downlink controlinformation (DCI). The DCI transports resource allocation informationand other control information for a UE or a UE group. For example, theDCI includes DL/UL scheduling information, UL transmit (Tx) powercontrol commands, etc.

The PDCCH delivers information about resource allocation and a transportformat for a downlink shared channel (DL-SCH), information aboutresource allocation and a transport format for an uplink shared channel(UL-SCH), paging information of a paging channel (PCH), systeminformation on the DL-SCH, information about resource allocation for ahigher-layer control message such as a random access responsetransmitted on the PDSCH, a set of transmit power control commands forindividual UEs of a UE group, Tx power control commands, voice overInternet protocol (VoIP) activation indication information, etc. Aplurality of PDCCHs may be transmitted in the control region. A UE maymonitor a plurality of PDCCHs. A PDCCH is transmitted on an aggregate ofone or more consecutive control channel elements (CCEs). A CCE is alogical allocation unit used to provide a PDCCH at a coding rate basedon the state of a radio channel. A CCE corresponds to a plurality ofresource element groups (REGs). The format of a PDCCH and the number ofavailable bits for the PDCCH are determined according to the number ofCCEs. An eNB determines a PDCCH format according to DCI transmitted to aUE and attaches a cyclic redundancy check (CRC) to control information.The CRC is masked with an identifier (ID) (e.g., a radio networktemporary identifier (RNTI)) according to the owner or use of the PDCCH.If the PDCCH is destined for a specific UE, the CRC may be masked with acell-RNTI (C-RNTI) of the UE. If the PDCCH carries a paging message, theCRC may be masked with a paging ID (P-RNTI). If the PDCCH carries systeminformation (particularly, a system information block (SIB)), the CRCmay be masked with a system information RNTI (SI-RNTI). If the PDCCH isdesignated as a random access response, the CRC may be masked with arandom access-RNTI (RA-RNTI).

FIG. 7 is a diagram illustrating an EPDCCH and a PDSCH scheduled by theEPDCCH.

Referring to FIG. 7, the EPDCCH may use a PDSCH region by defining apart of the PDSCH region in which data is generally transmitted and a UEshould perform a blind decoding operation to confirm whether an EPDCCHthereof is detected. The EPDCCH performs the same scheduling operationas a legacy PDCCH (i.e., PDSCH or PUSCH control). However, if the numberof UEs connected to a node such as a remote radio head (RRH) increases,more EPDCCHs are allocated to the PDSCH region and the number of blinddecoding operations that should be performed by the UE increases,thereby increasing complexity.

Hereinafter, a resource specific measurement scheme will be described.

As a method for reducing intercell interference, an intercellinterference cancellation scheme in the time domain has been proposed inwhich an aggressor cell uses a silent subframe (hereinafter, referred toas an almost blank subframe (ABS)) in which transmission power of aportion of physical channels is reduced or the physical channels are nottransmitted and a victim cell schedules the UE based on the silentsubframe. Generally, a subframe designated as the ABS is configured totransmit only a CRS.

In this case, an interference level greatly varies depending on asubframe in terms of the UE of the victim cell. In order to perform, ineach subframe, a more accurate radio link monitoring (RLM) operation, aradio resource management (RRM) operation of measuring reference signalreceived power (RSRP)/reference signal received quality (RSRQ), or CSImeasurement, the RLM operation/RRM operation should be limitedlyperformed in a set of subframes having a uniform interferencecharacteristic. Therefore, a current 3GPP LTE standard document definesa set of two CSI subframes for resource specific measurement.

Hereinafter, a transmission mode will be described.

The current 3GPP LTE standard document, specifically, 3GPP TS 36.213,defines DL transmission modes as shown in Tables 3 and 4 below. Thefollowing transmission modes may be configured for the UE through higherlayer signaling, i.e., RRC signaling.

TABLE 3 Transmission DCI Transmission scheme of PDSCH mode format SearchSpace corresponding to PDCCH Mode 1 DCI Common and Single-antenna port,port 0 format 1A UE specific by C- RNTI DCI UE specific by C-Single-antenna port, port 0 format 1 RNTI Mode 2 DCI Common and Transmitdiversity format 1A UE specific by C- RNTI DCI UE specific by C-Transmit diversity format 1 RNTI Mode 3 DCI Common and Transmitdiversity format 1A UE specific by C- RNTI DCI UE specific by C- Largedelay CDD (see clause 7.1.3) format 2A RNTI or Transmit diversity Mode 4DCI Common and Transmit diversity format 1A UE specific by C- RNTI DCIUE specific by C- Closed-loop spatial multiplexing (see format 2 RNTIclause 7.1.4) or Transmit diversity Mode 5 DCI Common and Transmitdiversity format 1A UE specific by C- RNTI DCI UE specific by C-Multi-user MIMO (see clause 7.1.5) format 1D RNTI Mode 6 DCI Common andTransmit diversity format 1A UE specific by C- RNTI DCI UE specific byC- Closed-loop spatial multiplexing (see format 1B RNTI clause 7.1.4)using a single transmission layer Mode 7 DCI Common and If the number ofPBCH antenna ports format 1A UE specific by C- is one, Single-antennaport, port 0 is RNTI used, otherwise Transmit diversity DCI UE specificby C- Single-antenna port, port 5 format 1 RNTI Mode 8 DCI Common and Ifthe number of PBCH antenna ports format 1A UE specific by C- is one,Single-antenna port, port 0 is RNTI used, otherwise Transmit diversityDCI UE specific by C- Dual layer transmission, port 7 and 8 format 2BRNTI (see clause 7.1.5A) or single-antenna port, port 7 or 8 Mode 9 DCICommon and UE Non-MBSFN subframe: If the format 1A specific by C-RNTInumber of PBCH antenna ports is one, Single-antenna port, port 0 isused, otherwise Transmit diversity MBSFN subframe: Single-antenna port,port 7 DCI UE specific by C- Up to 8 layer transmission, ports 7-14format 2C RNTI (see clause 7.1.5B) or single-antenna port, port 7 or 8 Mode 10 DCI Common and UE Non-MBSFN subframe: If the format 1A specificby C-RNTI number of PBCH antenna ports is one, Single-antenna port, port0 is used, otherwise Transmit diversity MBSFN subframe: Single-antennaport, port 7 DCI UE specific by C- Up to 8 layer transmission, ports7-14 format 2D RNTI (see clause 7.1.5B) or single-antenna port, port 7or 8

TABLE 4 Transmission DCI Search Transmission scheme of PDSCH mode formatSpace corresponding to EPDCCH Mode 1 DCI format UE Single-antenna port,port 0 1A specific by C- RNTI DCI format 1 UE Single-antenna port, port0 specific by C- RNTI Mode 2 DCI format UE Transmit diversity 1Aspecific by C- RNTI DCI format 1 UE Transmit diversity specific by C-RNTI Mode 3 DCI format UE Transmit diversity 1A specific by C- RNTI DCIformat UE Large delay CDD (see clause 7.1.3) or Transmit 2A specificdiversity by C- RNTI Mode 4 DCI format UE Transmit diversity 1A specificby C- RNTI DCI format 2 UE Closed-loop spatial multiplexing (see clause7.1.4) or specific Transmit diversity by C- RNTI Mode 5 DCI format UETransmit diversity 1A specific by C- RNTI DCI format UE Multi-user MIMO(see clause 7.1.5) 1D specific by C- RNTI Mode 6 DCI format UE Transmitdiversity 1A specific by C- RNTI DCI format UE Closed-loop spatialmultiplexing (see clause 7.1.4) using 1B specific a single transmissionlayer by C- RNTI Mode 7 DCI format UE If the number of PBCH antennaports is one, Single- 1A specific antenna port, port 0 is used,otherwise Transmit diversity by C- RNTI DCI format 1 UE Single-antennaport, port 5 specific by C- RNTI Mode 8 DCI format UE If the number ofPBCH antenna ports is one, Single- 1A specific antenna port, port 0 isused, otherwise Transmit diversity by C- RNTI DCI format UE Dual layertransmission, port 7 and 8 (see clause 7.1.5A) 2B specific orsingle-antenna port, port 7 or 8 by C- RNTI Mode 9 DCI format UENon-MBSFN subframe: If the number of PBCH 1A specific antenna ports isone, Single-antenna port, port 0 is by C- used, otherwise Transmitdiversity RNTI MBSFN subframe: Single-antenna port, port 7 DCI format UEUp to 8 layer transmission, ports 7-14 (see clause 7.1.5B) 2C specificor single-antenna port, port 7 or 8 by C- RNTI  Mode 10 DCI format UENon-MBSFN subframe: If the number of PBCH 1A specific antenna ports isone, Single-antenna port, port 0 is by C- used, otherwise Transmitdiversity RNTI MBSFN subframe: Single-antenna port, port 7 DCI format UEUp to 8 layer transmission, ports 7-14 (see clause 7.1.5B) 2D specificor single-antenna port, port 7 or 8 by C- RNTI

In the current 3GPP LTE standard document, a DCI format is definedaccording to the type of an RNTI masked to a PDCCH/EPDCCH. Particularly,in the case of a C-RNTI and an SPS C-RNTI, a transmission mode and a DCIformat corresponding to the transmission mode, i.e., a transmission modebased DCI format are defined. In addition, DCI format 1A capable ofbeing applied regardless of each transmission mode is also defined.Table 3 shows the case in which the type of the RNTI masked to the PDCCHis the C-RNTI and Table 4 shows the case in which the type of the RNTImasked to the EPDCCH is the C-RNTI. For the case in which the type ofthe RNTI masked to the PDCCH/EPCCH is the SPS C-RNTI, refer to theLTE/LTE-A standard document 36.213.

For example, in Table 3, if DCI format 1B is detected as a result ofblind-decoding the PDCCH masked with the C-RNTI in a UE specific searchspace, a PDSCH is decoded on the assumption that the PDSCH istransmitted by a closed-loop spatial multiplexing scheme using a singlelayer.

Hereinafter, CSI will be described.

Multiple input multiple output (MIMO) can be categorized into anopen-loop scheme and a closed-loop scheme. The open-loop scheme performsMIMO transmission at a transmitter without feedback of CSI from a MIMOreceiver, whereas the closed-loop scheme performs MIMO transmission atthe transmitter using feedback of CSI from the MIMO receiver. Inclosed-loop MIMO, each of the transmitter and the receiver may performbeamforming based on CSI to obtain multiplexing gain of MIMO transmitantennas. The transmitter (e.g., an eNB or a relay as an access DLtransmission entity) may allocate a UL control channel or a UL sharedchannel to the receiver (e.g., a UE or a relay as a backhaul DLreception entity) such that the receiver may feed back the CSI.

CSI fed back may include a rank indicator (RI), a precoding matrix index(PMI), and a channel quality indictor (CQI).

The RI indicates information about a channel rank. The channel rankrepresents a maximum number of layers (or streams) through whichdifferent pieces of information may be transmitted through the sametime-frequency resource. The RI is mainly determined by long term fadingof a channel and, thus, the RI may be fed back at a longer periodrelative to the PMI and CQI.

The PMI is information about a precoding matrix used for transmissionfrom the transmitter and is a value in which spatial characteristics ofa channel are reflected. Precoding refers to mapping of a transportlayer to a transmit antenna. A layer-to-antenna mapping relation may bedetermined by a precoding matrix. The PMI indicates a precoding matrixindex of an eNB preferred by a UE based on a metric such assignal-to-interference plus noise ratio (SINR). To reduce feedbackoverhead of precoding information, the transmitter and receiver mayshare a codebook including various precoding matrices and only an indexindicating a specific precoding matrix in the codebook may be fed back

The CQI is information indicating channel quality or channel strength.The CQI may be represented by an index corresponding to a combination ofpredetermined modulation and coding schemes (MCSs). That is, a feedbackCQI index may indicate a modulation scheme and a code rate. Generally,the CQI is a value reflecting a reception SINR capable of being obtainedwhen the eNB configures a spatial channel using the PMI.

In a system supporting an extended antenna configuration (e.g., LTE-Asystem), acquisition of additional multi-user diversity using multi-userMIMO (MU-MIMO) is considered. When an eNB performs DL transmission usingCSI fed back by one of multiple UEs, it is necessary to prevent DLtransmission from interfering with other UEs since an interferencechannel is present between UEs multiplexed in the antenna domain inMU-MIMO. Accordingly, in order to correctly perform MU-MIMO operation,more accurate CSI feedback than single user MIMO (SU-MIMO) needs to befed back.

A new CSI feedback scheme that improves CSI composed of the RI, PMI, andCQI may be applied in order to measure and report more accurate CSI. Forexample, precoding information fed back by the receiver may be indicatedby a combination of two PMIs. One (first PMI) of the two PMIs has longterm and/or wideband attributes and may be referred to as Wl. The otherPMI (second PMI) of the two PMIs has short term and/or subbandattributes and may be referred to as W2. A final PMI may be determinedby a combination (or function) of W1 and W2. For example, if the finalPMI is W, W may be defined as W=W1*W2 or W=W2*W1.

Hereinafter, CQI calculation will be described.

CQI calculation will be described in detail on the assumption that a DLreceiver is UE. A method of configuring/defining a resource which is areference for calculating a CQI when the UE reports CSI (hereinafter,referred to as a reference resource) will be described. First,definition of the CQI will be described in detail.

The CQI reported by the UE corresponds to a specific index value. A CQIindex is a value indicating a modulation scheme, a code rate, etc.corresponding to a channel state. For example, CQI indexes andinterpretation thereof may be given as shown in Table 5.

TABLE 5 CQI index modulation code rate × 1024 efficiency 0 out of range1 QPSK 78 0.1523 2 QPSK 120 0.2344 3 QPSK 193 0.3770 4 QPSK 308 0.6016 5QPSK 449 0.8770 6 QPSK 602 1.1758 7 16QAM 378 1.4766 8 16QAM 490 1.91419 16QAM 616 2.4063 10 64QAM 466 2.7305 11 64QAM 567 3.3223 12 64QAM 6663.9023 13 64QAM 772 4.5234 14 64QAM 873 5.1152 15 64QAM 948 5.5547

Based on an unrestricted observation interval in time and frequency, theUE may derive, for each CQI value reported in UL subframe n, the highestCQI index between CQI index 1 and CQI index 15 in Table 5 whichsatisfies a predetermined condition: A single PDSCH transport block witha combination of modulation scheme (e.g., MCS) and transport block size(TBS) corresponding to the CQI index, and occupying a group of DLphysical resource blocks termed a CSI reference resource, could bereceived with a transport block error probability not exceeding 0.1(i.e., 10%). If CQI index 1 does not satisfy the condition, UE maydetermine the CQI value as CQI index 0.

If CSI subframe sets C_(CSI,0) and C_(CSI,1) are configured by higherlayers, each CSI reference resource belongs to either C_(CSI,0) orC_(CSI,1) but not to both. When SCI subframe sets C_(CSI,0) andC_(CSI,1) are configured by higher layers, the UE is not expected toreceive a trigger for the CSI reference resource in a subframe that doesnot belong to either subframe set. For the UE in transmission mode 10and periodic CSI reporting, the CSI subframe set for the CSI referenceresource is configured by higher layers for each CSI process.

For the UE in transmission mode 9 when parameter pmi-RI-Report isconfigured by higher layers, the UE may derive channel measurements forcomputing the CQI value reported in UL subframe n based on onlyCSI-reference signals (CSI-RSs) for which the UE is configured to assumenon-zero power. For the UE in transmission mode 9 when the parameterpmi-RI-Report is not configured by higher layers or in transmissionmodes 1 to 8, the UE may derive the channel measurements for computingCQI based on a CRS.

For the UE in transmission mode 10, the UE may derive the channelmeasurements for computing the CQI value reported in UL subframe n andcorresponding to a CSI process, based on only the non-zero power CSI-RSwithin a configured CSI-RS resource associated with the CSI process.

For the UE in transmission mode 10, the UE may derive the interferencemeasurements for computing the CQI value reported in UL subframe n andcorresponding to a CSI process, based on only the zero power CSI-RSwithin the configured CSI-interference measurement (CSI-IM) resourceassociated with the CSI process. If the UE in transmission mode 10 isconfigured by higher layers for CSI subframe sets C_(CSI,0) andC_(CSI,1) for the CSI process, the configured CSI-IM resource within thesubframe subset belonging to the CSI reference resource is used toderive the interference measurement.

A combination of modulation scheme and transport block size correspondsto a CQI index if all of the following conditions are satisfied, thatis, if i) the combination could be signaled for transmission on thePDSCH in the CSI reference resource according to the relevant TBS table,ii) the modulation scheme is indicated by the CQI index, and iii) thecombination of TBS and modulation scheme when applied to the referenceresource results in an effective channel code rate which is as close aspossible to the code rate indicated by the CQI index. If more than twocombinations of TBS and modulation scheme results in an effectivechannel code rate equally close to the code rate indicated by the CQIindex, only the combination with the smallest of such TBSs is relevant.

Meanwhile, a CQI reference resource is defined as follows.

In the frequency domain, the CSI reference resource is defined by thegroup of DL physical resource blocks corresponding to the band to whichthe derived CQI value relates.

In the time domain, for the UE configured in transmission modes 1 to 9or transmission mode 10 with a single configured CSI process for theserving cell, the CQI reference resource is defined by a single DLsubframe n-n_(CQI) _(_) _(ref). In this case, for periodic CQI reportingn-n_(CQI) _(_) _(ref) f is the smallest value greater than or equal to4, such that it corresponds to a valid DL subframe and, for aperiodicCQI reporting n-n_(CQI) _(_) _(ref) is the same DL subframe as the validDL subframe corresponding to a CQI request (or in which the CQI requestis received) in a UL DCI format (i.e., a PDCCH DCI format for providingUL scheduling control information to the UE). In addition, for aperiodicCQI reporting n-n_(CQI) _(_) _(ref) is equal to 4 and DL subframen-n_(CQI) _(_) _(ref) corresponds to a valid DL subframe, in which DLsubframe n-n_(CQI) _(_) _(ref) is received after the subframe with thecorresponding CQI request (or in which the CQI request is received) in arandom access response grant.

In the time domain, for a UE configured in transmission mode 10 withmultiple configured CSI processes for the serving cell, the CQIreference resource is defined by a single DL subframe n-n_(CQI) _(_)_(ref) .

In this case, for FDD and periodic or aperiodic CQI reporting, n-n_(CQI)_(_) _(ref) is the smallest value greater than or equal to 5, such thatit corresponds to a valid DL subframe, and, for aperiodic CSI reporting,the corresponding CSI request is in a UL DCI format. For FDD andaperiodic CQI reporting, n-n_(CQI) _(_) _(ref) is equal to 5 andDLsubframe n-n_(CQI) _(_) _(ref) corresponds to a valid DL subframe (orin which the CQI request is received), where DL subframe n-n_(CQI) _(_)_(ref) is received after the subframe with the corresponding CQI requestin a random access response grant.

For TDD, and 2 or 3 configured CSI processes, and periodic or aperiodicCSI reporting, n-n_(CQI) _(_) _(ref) is the smallest value greater thanor equal to 4, such that it corresponds to a valid DL subframe and, foraperiodic CSI reporting, the corresponding CSI request is in a UL DCIformat. For TDD, and 2 or 3 configured CSI processes, and aperiodic CSIreporting, n-n_(CQI) _(_) _(ref) is equal to 4 and DL subframe n-n_(CQI)_(_) _(ref) corresponds to a valid DL subframe, where DL subframen-n_(CQI) _(_) _(ref) is received after the subframe with thecorresponding CQI request (or in which the CQI request is received) in arandom access response grant.

For TDD, and 4 configured CSI processes, and periodic or aperiodic CSIreporting, n_(CQI) _(_) _(ref) is the smallest value greater than orequal to 5, such that it corresponds to a valid DL subframe and, foraperiodic CSI reporting, the corresponding CSI request is in a UL DCIformat. For TDD, and 4 configured CSI processes, and aperiodic CSIreporting, n_(CQI) _(_) _(ref) is equal to 5 and DL subframe n-n_(CQI)_(_) _(ref) corresponds to a valid DL subframe, where DL subframen-n_(CQI) _(_) _(ref) is received after a subframe with thecorresponding CSI request in a random access response grant.

The valid DL subframe means a DL subframe corresponding to the case inwhich the DL subframe is configured for the corresponding UE, the DLframe is not a multicast broadcast single frequency network (MBSFN)subframe except for transmission mode 9 or 10, the DL subframe does notcontain a DwPTS field when the length of DwPTS is 7680*Ts(Ts=1/(15000×2048) seconds) or less, and the DL subframe does not fallwithin a configured measurement gap for the UE. For periodic CSIreporting, the DL subframe is an element of the CSI subframe set linkedwith the periodic CSI report and, for a UE configured in transmissionmode 10 with multiple configured CSI processes, aperiodic CSI reportingfor a CSI process, the DL subframe is an element of the CSI subframe setlinked with the periodic CSI report, and for a UE configured with a CSIsubframe set for a CSI process, the DL subframe is an element of the CSIsubframe set linked with the DL subframe with the CSI request in a ULDCI format.

If there is no valid DL subframe for the CQI reference resource, CQIreporting may be omitted in UL subframe n.

In the layer domain, the CQI reference resource is defined by any RI andPMI based on which the CQI is calculated.

In the CSI reference resource, the UE may assume the following for thepurpose of deriving the CQI index: (1) The first 3 OFDM symbols of a DLsubframe are used for control signaling; (2) No resource elements areused by primary or secondary synchronization signals or PBCH; (3) CPlength of the non-MBSFN subframes; (4) Redundancy version is 0; (5) IfCSI-RS is used for channel measurements, the ratio of PDSCH energy perresource element (EPRE) to CSI-RS EPRE is given as a predetermined valueby higher layers; (6) A PDSCH transmission scheme (single antenna porttransmission, transmission diversity, spatial multiplexing, MU-MIMO,etc.) defined for each transmission mode is currently configured for theUE (which may be a default mode); (7) If CRS is used for channelmeasurements, the ratio of PDSCH EPRE to cell-specific RS EPRE isdetermined according to a predetermined condition; and (8) The PDSCHtransmission scheme is given by Table 6 depending on the transmissionmode currently configured for the UE.

TABLE 6 Transmission Mode Transmission Scheme of PDSCH 1 Single-antennaport, port 0 2 Transmit diversity 3 Transmit diversity if the associatedrank indicator is 1, otherwise large delay CDD 4 Closed-loop spatialmultiplexing 5 Multi-user MIMO 6 Closed-loop spatial multiplexing with asingle transmission layer 7 If the number of PBCH antenna ports is one,Single- antenna port, port 0; otherwise Transmit diversity 8 If the UEis configured without PMI/RI reporting: if the number of PBCH antennaports is one, single-antenna port, port 0; otherwise transmit diversityIf the UE is configured with PMI/RI reporting: closed- loop spatialmultiplexing 9 If the UE is configured without PMI/RI reporting: if thenumber of PBCH antenna ports is one, single-antenna port, port 0;otherwise transmit diversity If the UE is configured with PMI/RIreporting: if the number of CSI-RS ports is one, single-antenna port,port 7; otherwise up to 8 layer transmission, ports 7-14 (see subclause7.1.5B [1]) 10 If a CSI process of the UE is configured without PMI/RIreporting: if the number of CSI-RS ports is one, single- antenna port,port7; otherwise transmit diversity If a CSI process of the UE isconfigured with PMI/RI reporting: if the number of CSI-RS ports is one,single- antenna port, port 7; otherwise up to 8 layer transmission,ports 7-14 (see subclause 7.1.5B [1])

For details of CQI definition including CSI reporting in the case inwhich PMI/RI reporting is not configured, reference may be made to 3GPPTS36.213.

Based on the above description, the present invention proposes a methodof stably supporting channel estimation and reporting operations of a UEregardless of whether the UE has successfully received a radio resourcereconfiguration message, in the case in which a plurality of cellsdynamically changes usage of a radio resource according to a systemoverhead state of the cells and informs the UE of information aboutchange of usage of the radio resource through a reconfiguration messageof a predefined format.

The reconfiguration message may be defined by a higher layer signalingformat (e.g., SIB/PBCH/MAC/RRC) or a physical layer signaling format(e.g., PDCCH/EPDCCH/PDSCH) and may have a UE-specific, a cell-specific,UE-group-specific, or UE-group-common characteristic. Additionally, thereconfiguration message may be transmitted through a UE-specific searchspace (USS) or a common search space (CSS).

For convenience of description, embodiments of the present inventionwill be described based on a 3GPP LTE system. However, the range of asystem to which the present invention is applied may be extended toother systems in addition to the 3GPP LTE system.

The embodiments of the present invention may be extended to the case ofdynamically changing a resource on a specific cell or a specificcomponent carrier (CC) according to a system overhead state in anenvironment to which carrier aggregation (CA) is applied. Theembodiments of the present invention may also be extended to the case ofdynamically changing usage of a radio resource in a TDD system, an FDDsystem, or a TDD/FDD combination system. For convenience of descriptionof the embodiments, it will be assumed hereinbelow that each cell in aTDD system environment dynamically changing usage of a legacy radioresource according to a system overhead state of the cell.

Legacy radio resources may be classified into two types of resources dueto dynamic change of usage of the radio resources.

For example, the legacy radio resources may be classified into aresource set used for static (i.e., fixed) usage and a resource set,usage of which is dynamically changed, (i.e., flexible resources). As anexample, a resource set which is used (or which has been used) as thesame usage as UL-DL configuration of an SIB may be defined as a staticresource set and a resource set which is used (or which has aprobability of being used) as different usage from UL-DL configurationof the SIB may be defined as a flexible resource set.

As another example, a resource set which is used (or which has beenused) as the same usage as UL-DL configuration configured at a previoususage change timing (e.g., a usage change scheme based on a predefinedreconfiguration period) may be defined as the static resource set and aresource set which is used (or which has a probability of being used) asdifferent usage from UL-DL configuration configured at the previoususage change timing may be defined as the flexible resource set

As still another example, a resource set which is used (or which hasbeen used) as the same usage as UL-DL configuration of a predefinedreference DL HARQ timeline (or UL-DL configuration of reference UL HARQtimeline) may be defined as the static resource set and a resource setwhich is used (or which has a probability of being used) as differentusage from UL-DL configuration of the reference DL HARQ timeline (orUL-DL configuration of the reference UL HARQ timeline) may be defined asthe flexible resource set.

In this case, the reference DL/UL HARQ timeline is a timeline configuredfor the purpose of stably maintaining a HARQ timeline regardless of(re)change of UL-DL configuration and may be defined as a DL/UL HARQtimeline of UL-DL configuration including at least one of i) a union ofDL subframes /an intersection of UL subframes, ii) a unit of DLsubframes/a union of UL subframes, iii) an intersection of DL subframes/an intersection of UL subframes, and iv) an intersection of DLsubframes /a union of UL subframes of reconfigurable UL-DL configurationcandidates.

FIG. 8 illustrates the case in which legacy subframes are classifiedinto a static subframe set and a flexible subframe set in a TDD systemenvironment. In FIG. 8, it is assumed that a legacy UL-DL configurationconfigured through an SIB signal is UL-DL configuration #1 (i.e.,DSUUDDSUUD) and an eNB informs a UE of reconfiguration information ofusage of a radio resource through a predefined signal.

The radio resource reconfiguration message is used, according to apredefined rule, to indicate usage of radio resources appearing i) aftera timing including a reconfiguration message reception timing, ii) aftera timing excluding the reconfiguration message reception timing, or iii)at a timing a predefined time after the reconfiguration messagereception timing (i.e., after a subframe offset).

Therefore, in order to perform stable DL/UL communication of a systemand derive and report stable CSI by a UE, a method oftransmitting/receiving the reconfiguration message with a high successprobability or UL-DL configuration (i.e., a fallback operation for UL-DLconfiguration) assumed by a specific UE in the case in which the UE hasnot successfully received the reconfiguration message needs to bedefined. The case in which the UE has not successfully received thereconfiguration message may include, for example, the case in which aresult of cyclic redundancy check (CRC) for the received reconfigurationmessage is determined to be false or the case in which the UE misses thereconfiguration message (e.g., the case in which the UE misses thereconfiguration message due to a discontinuous reception (DRX)operation).

FIG. 9 illustrates the case in which an ambiguity problem as to whichassumption/rule about UL-DL configuration is based on to determine thelocation of a valid CSI reference resource linked with CSI reporting ofa specific timing occurs due to reception failure of a reconfigurationmessage by a UE.

In FIG. 9, it is assumed that a periodic CSI reporting operation isconfigured (e.g., a period of 5 ms) and corresponding periodic CSIreporting is performed through a static UL resource. It is also assumedthat a legacy UL-DL configuration configured through an SIB signal isUL-DL configuration #0 (i.e., DSUUUDSUUU) and an eNB transmits thereconfiguration message based on a predefined period (e.g., 10 ms) and apredefined signal format. It is assumed that the UE has not successfullyreceived the reconfiguration message transmitted in subframe #(n+10) andthus the UE cannot clearly recognize usage of subframes starting fromsubframe #(n+10), usage of which is determined by the reconfigurationmessage, to subframe #(n+19).

For the cases of FIG. 9(a) to FIG. 9(d), a CSI reporting timing and thelocation of a valid CSI reference resource linked with CSI reportingwill now be described.

-   Case A: A description is given with reference to FIG. 9(a).-   CSI reporting timing: belongs to a duration during which resource    usage is determined from a successfully received reconfiguration    message.-   The location of a valid CSI reference resource linked with CSI    reporting: belongs to a duration during which resource usage is    determined from a successfully received reconfiguration message.-   Case B: A description is given with reference to FIG. 9(b).-   CSI reporting timing: belongs to a duration during which resource    usage is determined from a reception failed reconfiguration message.-   The location of a valid CSI reference resource linked with CSI    reporting: belongs to a duration during which resource usage is    determined from a successfully received reconfiguration message.-   Case C: A description is given with reference to FIG. 9(c).-   CSI reporting timing: belongs to a duration during which resource    usage is determined from a reception failed reconfiguration message.-   The location of a valid CSI reference resource linked with CSI    reporting: belongs to a duration during which resource usage is    determined from a reception failed reconfiguration message.-   Case D: A description is given with reference to FIG. 9(d).-   CSI Reporting Timing: Belongs to a Duration During Which Resource    Usage is Determined from a Successfully Received Reconfiguration    Message-   The location of a valid CSI reference resource linked with CSI    reporting: belongs to a duration during which resource usage is    determined from a reception failed reconfiguration message.

CSI Reporting Configuration of UE Independent of Whether ReconfigurationMessage has been Received

In the above-described cases of FIG. 9 (i.e., Case A, Case B, Case C,and Case D), at least one of rules for i) configuration for determiningthe location of a valid CSI reference resource linked with CSI reportingof a specific timing, ii) configuration for a condition that should besatisfied to be considered as the valid CSI reference resource, and iii)an assumption about UL-DL configuration used to determine the locationof the valid CSI reference resource needs to be (re)defined regardlessof whether the reconfiguration message has been successfully received inorder to derive and report stable CSI by a UE. That is, due to receptionfailure of the reconfiguration message by the UE, in the above-describedcases of FIG. 9 (i.e., Case A, Case B, Case C, and Case D), an ambiguityproblem as to whether CSI reporting should be (actually) performed, anambiguity problem as to how the location of the valid CSI referenceresource linked with CSI reporting of a specific timing should bedetermined, and/or an ambiguity problem as to which assumption aboutUL-DL configuration should be made to determine the location of thevalid CSI reference resource may occur.

Further, in the above-described cases of FIG. 9 (i.e., Case A, Case B,Case C, and Case D), the location of the valid CSI reference resourcelinked with CSI reporting of a specific timing may be regarded as one ofi) the nearest subframe which corresponds to a previous timing includinga predetermined value (e.g., 4 ms or 5 ms) starting from the CSIreporting timing and simultaneously satisfies a condition of apredefined valid CSI reference resource, ii) a subframe whichcorresponds to a timing prior to the predefined value starting from theCSI reporting timing and simultaneously satisfies the condition of thepredefined valid CSI reference resource (e.g., aperiodic CSI reportingbased on a CSI request filed of a random access response (RAR) grant),and iii) a subframe in which a CSI request field of a UL DCI format fortriggering CSI reporting is received and simultaneously the condition ofthe predefined valid CSI reference resource is satisfied (e.g.,aperiodic CSI reporting).

Therefore, the present invention proposes a method of guaranteeingstable CSI derivation and reporting of the UE regardless of whether theUE has successfully received a radio resource reconfiguration message,in the case in which a plurality of cells dynamically changes usage of aradio resource according to a system overhead state of the cells andinforms the UE of information about change of usage of the radioresource through a reconfiguration message of a predefined format.

As an example, in order to guarantee stable CSI derivation and reportingof the UE in the above-described cases (i.e., Case A, Case B, Case C,and Case D of FIG. 9), a rule for determining the location of the validCSI reference resource linked with CSI reporting of a specific timing, arule for a condition that should be satisfied to be considered as thevalid CSI reference resource, and/or a rule for an assumption aboutUL-DL configuration used to determine the location of the valid CSIreference resource (i.e., a fallback operation of UL-DL configuration)needs to be (re)defined

In addition, the location of the valid CSI reference resource linkedwith CSI reporting of a specific timing may be regarded as the nearestsubframe which corresponds to a previous timing including apredetermined value starting from a CSI reporting timing andsimultaneously satisfies a condition of a predefined valid CSI referenceresource, a subframe which corresponds to a timing prior to thepredefined value starting from the CSI reporting timing andsimultaneously satisfies the condition of the predefined valid CSIreference resource, or a subframe in which a CSI request field of a ULDCI format for triggering CSI reporting is received and simultaneouslythe condition of the predefined valid CSI reference resource issatisfied.

Embodiments described below may be extensively applied to a situation inwhich periodic CSI reporting operation is configured and/or a situationin which aperiodic CSI reporting operation is triggered. The embodimentsmay also be extensively applied to a situation in which varioustransmission modes (TMs) (e.g., TMs 1 to 9 or TM 10) are configuredand/or a situation in which various numbers of CSI processes (e.g., 1,2, 3, and 4 CSI processes) are configured.

First Embodiment

According to the first embodiment of the present invention, the locationof a valid CSI reference resource linked with CSI reporting of aspecific timing may be determined based on an assumption about aspecific UL-DL configuration among UL-DL configurations (i.e., Options#A to #D) numerated below.

-   [Option #A] UL-DL configuration of an SIB-   [Option #B] UL-DL configuration of a predefined reference UL HARQ    timeline-   [Option #C] UL-DL configuration of a predefined reference DL HARQ    timeline-   [Option #D] UL-DL configuration (re)configured by a reconfiguration    message

In addition, it will be assumed hereinbelow that a condition of thevalid CSI reference resource is a DL subframe and/or a special subframe(e.g., DwPTS). However, in this embodiment, when a specific TM (e.g., TM10) is configured and/or the reconfiguration message has a physicallayer signal format (e.g., explicit L1 signaling of reconfiguration by aUE-group-common (e)PDCCH), the condition of the valid CSI referenceresource may not be limited to the DL subframe and/or the specialsubframe (e.g., all of the DL subframe (and/or the special subframe(e.g., DwPTS)) and a UL subframe (and/or a special subframe (e.g.,UpPTS)) may be considered).

While an assumption about UL-DL configuration used to determine thelocation of the valid CSI reference resource according to the firstembodiment may be commonly applied to Case A, Case B, Case C, and Case Ddescribed with reference to FIG. 9, the assumption about UL-DLconfiguration may be independently applied to Case A, Case B, Case C,and Case D (e.g., an assumption about UL-DL configuration applied tosome cases (e.g., Case C) is different from an assumption about UL-DLconfiguration applied to the other cases (e.g., Case A, Case B, and CaseD)).

Hereinafter, for convenience of description of the present invention, itwill be assumed that a reconfiguration message of a specific timing hasnot been successfully received in a situation in which the location ofthe valid CSI reference resource is determined based on a DL subframe(and/or special subframe (e.g., DwPTS)) of UL-DL configuration(re)configured by the reconfiguration message (i.e., Option #D).However, it is apparent that the present invention may be extended tothe case in which the reconfiguration message of a specific timing hasnot been successfully received in a situation in which the assumptionabout UL-DL configuration used to determine the location of the validCSI reference resource is defined in a different form from the abovecase (e.g., in Option #C).

That is, i) in a situation in which the location of the valid CSIreference resource is determined based on the DL subframe (and/or thespecial subframe (e.g., DwPTS)) of UL-DL configuration (re)configured bythe reconfiguration message or ii) in a situation in which the locationof the valid CSI reference resource is determined based on the DLsubframe (and/or special subframe (e.g., DwPTS)) of UL-DL configurationof a predefined reference DL HARQ timeline, if the reconfigurationmessage of a specific timing has not been successfully received, anassumption about UL-DL configuration used to determine the location ofthe valid CSI reference resource and a subframe satisfying the conditionof the valid CSI reference resource with respect to each case may beconfigured as Embodiment 1-1 to Embodiment 1-15 described below.

Embodiment 1-1

According to the present invention, if the location of the valid CSIreference resource linked with CSI reporting of a specific timingbelongs to a duration during which resource usage is determined from areception failed reconfiguration message (i.e., Case C or Case D of FIG.9), the location of the valid CSI reference resource linked with CSIreporting of a specific timing may be determined in consideration ofonly DL subframes and/or special subframes (e.g., DwPTS) of UL-DLconfiguration (i.e., [Option #A]) of an SIB.

Embodiment 1-2

According to the present invention, if the location of the valid CSIreference resource linked with CSI reporting of a specific timingbelongs to a duration during which resource usage is determined from areception failed reconfiguration message (i.e., Case C or Case D), thelocation of the valid CSI reference resource linked with CSI reportingof a specific timing may be determined in consideration of only DLsubframes and/or special subframes (e.g., DwPTS) of UL-DL configuration(i.e., [Option #B]) of a predefined reference UL HARQ timeline.

Embodiment 1-3

According to the present invention, if the location of the valid CSIreference resource linked with CSI reporting of a specific timingbelongs to a duration during which resource usage is determined from areception failed reconfiguration message (i.e., Case C or Case D), thelocation of the valid CSI reference resource linked with CSI reportingof a specific timing may be determined in consideration of only DLsubframes and/or special subframes (e.g., DwPTS) of UL-DL configuration(i.e., [Option #C]) of a predefined reference DL HARQ timeline.

Embodiment 1-4

According to the present invention, if the location of the valid CSIreference resource linked with CSI reporting of a specific timingbelongs to a duration during which resource usage is determined from areception failed reconfiguration message (i.e., Case C or Case D), thelocation of the valid CSI reference resource linked with CSI reportingof a specific timing may be determined in consideration of only DLsubframes and/or special subframes (e.g., DwPTS) of a (predefined)static resource set.

Embodiment 1-5

According to the present invention, if the location of the valid CSIreference resource linked with CSI reporting of a specific timingbelongs to a duration during which resource usage is determined from areception failed reconfiguration message (i.e., Case C or Case D), thelocation of the valid CSI reference resource linked with CSI reportingof a specific timing may be determined in consideration of only DLsubframes and/or special subframes (e.g., DwPTS) of a duration duringwhich resource usage is determined from a latest successfully receivedreconfiguration message.

Embodiment 1-6

According to the present invention, if the location of the valid CSIreference resource linked with CSI reporting of a specific timingbelongs to a duration during which resource usage is determined from areception failed reconfiguration message (i.e., Case C or Case D), CSIreporting may be omitted or CSI reporting may be performed using aspecific predefined value (e.g., RI/PMI/CQI).

A method of omitting CSI reporting according to Embodiment 1-6 may belimitedly applied only to the case in which an eNB is configured toreceive feedback (e.g., ACK/NACK information) as to whether thereconfiguration message has been successfully received from a UE. Thisis because, if the eNB cannot recognize information as to whether anindividual UE has successfully received the reconfiguration message, theeNB does not accurately discern whether the UE has performed CSIreporting and/or whether rate matching has been applied to UL datamapping due to piggybacking of CSI on a PUSCH.

Embodiment 1-7

According to the present invention, if the location of the valid CSIreference resource linked with CSI reporting of a specific timingbelongs to a duration during which resource usage is determined from areception failed reconfiguration message (i.e., Case C or Case D), theCSI reporting may be performed using a latest successfully reported CSIvalue.

In this case, the latest successfully reported CSI value may be definedas one of i) a recent CSI reporting value based on DL subframes and/orspecial subframes (e.g., DwPTS) of a duration during which resourceusage is determined from a latest successfully received reconfigurationmessage, ii) a recent CSI reporting value based on DL subframes and/orspecial subframes (e.g., DwPTS) of UL-DL configuration of an SIB, iii) arecent CSI reporting value based on DL subframes and/or specialsubframes (e.g., DwPTS) of UL-DL configuration of a predefined referenceUL HARQ timeline, iv) a recent CSI reporting value based on DL subframesand/or special subframes (e.g., DwPTS) of UL-DL configuration of apredefined reference DL HARQ timeline, and v) a recent CSI reportingvalue based on DL subframes and/or special subframes (e.g., DwPTS) of a(predefined) static resource set.

Embodiment 1-8

According to the present invention, if the location of the valid CSIreference resource linked with CSI reporting of a specific timingbelongs to a duration during which resource usage is determined from areception failed reconfiguration message (i.e., Case C or Case D), CSIreporting may be performed (re)using a valid CSI reference resource oflatest successfully performed CSI reporting.

For example, the latest successfully performed CSI reporting may bedefined as one of i) recent CSI reporting based on DL subframes and/orspecial subframes (e.g., DwPTS) of a duration during which resourceusage is determined from a latest successfully received reconfigurationmessage, ii) recent CSI reporting based on DL subframes and/or specialsubframes (e.g., DwPTS) of UL-DL configuration of an SIB, iii) recentCSI reporting based on DL subframes and/or special subframes (e.g.,DwPTS) of UL-DL configuration of a predefined reference UL HARQtimeline, iv) recent CSI reporting based on DL subframes and/or specialsubframes (e.g., DwPTS) of UL-DL configuration of a predefined referenceDL HARQ timeline, and v) recent CSI reporting based on DL subframesand/or special subframes (e.g., DwPTS) of a (predefined) static resourceset.

Further, if Embodiment 1-8 is applied in a situation in which TM 10 isconfigured, a latest successfully performed CSI reporting value and aCSI reporting value of a specific timing (after) (re)using a valid CSIreference resource of latest successfully performed CSI reporting mayhave different values.

That is, since the CSI reporting value of a specific timing (after)(re)using the valid CSI reference resource of latest successfullyperformed CSI reporting is a result of interpolatingchannel/interference in the valid CSI reference resource (i.e., thevalid CSI reference resource of latest successfully performed CSIreporting) based on measurement information additionally obtained afterthe valid CSI reference resource of latest successfully performed CSIreporting, the CSI reporting value of a specific timing (after)(re)using the valid CSI reference resource of latest successfullyperformed CSI reporting may be different from the latest successfullyperformed CSI reporting value.

Embodiment 1-9

According to the present invention, if the location of the valid CSIreference resource linked with CSI reporting of a specific timingbelongs to a duration during which resource usage is determined from areception failed reconfiguration message (i.e., Case C or Case D), validCSI reference resources may be regarded as being absent in a durationduring which resource usage is determined from the reception failedreconfiguration message.

For example, when Embodiment 1-9 is applied, the location of the validCSI reference resource linked with CSI reporting of a specific timingmay be determined in consideration of only i) DL subframes and/orspecial subframes (e.g., DwPTS) of a duration during which resourceusage is determined from a latest successfully received reconfigurationmessage, ii) DL subframes and/or special subframes (e.g., DwPTS) of aduration during which resource usage is determined from the latestsuccessfully received reconfiguration message and simultaneously DLsubframes and/or special subframes (e.g., DwPTS) of UL-DL configurationof an SIB, iii) DL subframes and/or special subframes (e.g., DwPTS) of aduration during which resource usage is determined from the latestsuccessfully received reconfiguration message and simultaneously DLsubframes and/or special subframes (e.g., DwPTS) of UL-DL configurationof a predefined reference UL HARQ timeline, iv) DL subframes and/orspecial subframes (e.g., DwPTS) of a duration during which resourceusage is determined from the latest successfully receivedreconfiguration message and simultaneously DL subframes and/or specialsubframes (e.g., DwPTS) of UL-DL configuration of a predefined referenceDL HARQ timeline, or v) DL subframes and/or special subframes (e.g.,DwPTS) of a duration during which resource usage is determined from thelatest successfully received reconfiguration message and simultaneouslyDL subframes and/or special subframes (e.g., DwPTS) of a (predefined)static resource set.

When Embodiment 1-9 is applied, Embodiments 1 to 9 may be combined withone of Embodiments 1-6, 1-7, and 1-8 may be applied.

Embodiment 1-10

According to the present invention, if the location of the valid CSIreference resource linked with CSI reporting of a specific timingbelongs to a duration during which resource usage is determined from areception failed reconfiguration message (i.e., Case C or Case D) andEmbodiment 1-1 to Embodiment 1-9 of the present invention are applied,subframes except for subframes satisfying a condition of a predefinedvalid CSI reference resource are regarded as an invalid CSI referenceresource (e.g., a UL subframe and/or UpPTS of a special subframe).

Embodiment 1-11

According to the present invention, if the location of the valid CSIreference resource linked with CSI reporting of a specific timingbelongs to a duration during which resource usage is determined from thesuccessfully received reconfiguration message (i.e., Case A or Case B),the location of the valid CSI reference resource linked with CSIreporting of a specific timing may be determined in consideration ofonly DL subframes and/or special subframes (e.g., DwPTS) of a durationduring which resource usage is determined from the reconfigurationmessage.

Embodiment 1-12

According to the present invention, if the location of the valid CSIreference resource linked with CSI reporting of a specific timingbelongs to a duration during which resource usage is determined from thesuccessfully received reconfiguration message (i.e., Case A or Case B),one of Embodiment 1-1 to Embodiment 1-4 described above may be applied.For a description of the above case, refers to the contents described inEmbodiment 1-1 to Embodiment 1-4.

Embodiment 1-13

According to the present invention, if a CSI reporting timing belongs toa duration during which resource usage is determined from a receptionfailed reconfiguration message, a specific embodiment of Embodiment 1-1to Embodiment 1-5 may be applied. For a detailed description, refer tothe contents described in Embodiment 1-1 to Embodiment 1-5.

The location of the valid CSI reference resource linked with CSIreporting of a corresponding timing may be configured to be determinedin consideration of only i) DL subframes and/or special subframes (e.g.,DwPTS) of UL-DL configuration of an SIB, ii) DL subframes and/or specialsubframes (e.g., DwPTS) of UL-DL configuration of a predefined referenceUL HARQ timeline, iii) DL subframes and/or special subframes (e.g.,DwPTS) of UL-DL configuration of a predefined reference DL HARQtimeline, iv) DL subframes and/or special subframes (e.g., DwPTS) of apredefined static resource set, or v) DL subframes and/or specialsubframes (e.g., DwPTS) of a duration during which resource usage isdetermined from a successfully received reconfiguration message.

Determination of the location of the valid CSI reference resource linkedwith CSI reporting of a corresponding timing based on one of Embodiment1-1 to Embodiment 1-4 is effective i) when communication is limitedlyperformed only in DL subframes and/or special subframes (e.g., DwPTS) ofUL-DL configuration of an SIB in a duration during which resource usageis determined from a reception failed reconfiguration message, ii) whencommunication is limitedly performed only in DL subframes and/or specialsubframes (e.g., DwPTS) of UL-DL configuration of a predefined referenceUL HARQ timeline, iii) when communication is limitedly performed only inDL subframes and/or special subframes (e.g., DwPTS) of UL-DLconfiguration of a predefined reference DL HARQ timeline, or iv) whencommunication is limitedly performed only in DL subframes and/or specialsubframes (e.g., DwPTS) of a (predefined) static resource set.

This is because the eNB may obtain a CSI value based on a valid CSIreference resource having the same or similar interferencecharacteristic as or to DL communication actually performed in theduration during which resource usage is determined from the receptionfailed reconfiguration message.

Embodiment 1-14

According to the present invention, if a CSI reporting timing belongs toa duration during which resource usage is determined from a receptionfailed reconfiguration message, a specific embodiment of Embodiment 1-6to Embodiment 1-9 may be applied. For a detailed description, refer tothe contents described in Embodiment 1-6 to Embodiment 1-9.

For example, if a CSI reporting timing belongs to a duration duringwhich resource usage is determined from the reception failedreconfiguration message, i) corresponding

CSI reporting is omitted, ii) corresponding CSI reporting is performedusing a specific predefined value (e.g., RI/PMI/CQI), iii) correspondingCSI reporting is performed using a latest successfully reported CSIvalue, iv) corresponding CSI reporting is performed (re)using a validCSI reference resource of latest successfully performed CSI reporting,or v) valid CSI reference resources are regarded as being absent in aduration during which resource usage is determined from the receptionfailed reconfiguration message.

Aperiodic CSI Reporting in Case of Failing to Receive ReconfigurationMessage

The present invention also proposes a method of stably guaranteeingaperiodic CSI reporting based on a CSI request field of a random accessresponse (RAR) grant when a reconfiguration message of a specific timinghas not been successfully received in a situation in which the locationof a valid CSI reference resource is configured to be determined basedon a DL subframe and/or a specific subframe (e.g., DwPTS) of UL-DLconfiguration (re)configured by the reconfiguration message. However, itis apparent that the present invention may be extended to the case inwhich the reconfiguration message of the specific timing has not beensuccessfully received in a situation in which an assumption about aUL-DL configuration used to determine the location of the valid CSIreference resource is defined in a different form (e.g., Option #A,Option #B, or Option #C) from the above case.

Legacy aperiodic CSI reporting based on the CSI request field of the RARgrant is performed based on a subframe which corresponds to a timingprior to a predefined value (e.g., 4 ms or 5 ms) and simultaneouslysatisfies the condition of a predefined valid CSI reference resource asa corresponding CSI reporting timing. However, since usage of subframesdetermined by the reconfiguration message is not clearly recognized dueto reception failure of the reconfiguration message, an ambiguityproblem as to whether corresponding aperiodic CSI reporting should be(actually) performed, an ambiguity problem how to determine the locationof the valid CSI reference resource linked with corresponding aperiodicCSI reporting, or an ambiguity problem as to which assumption aboutUL-DL configuration is based on to determine the location of the validCSI reference resource of corresponding aperiodic CSI reporting occurs.

Accordingly, in order to stably guarantee aperiodic CSI reporting basedon the CSI request field of the RAR grant, an assumption about UL-DLconfiguration used to determine the location of the valid CSI referenceresource (linked with corresponding aperiodic CSI reporting) and asubframe satisfying the condition of the valid CSI reference resourcemay be configured as in Embodiment 1-15 to Embodiment 1-18 describedbelow.

Embodiment 1-15

According to the present invention, aperiodic CSI reporting based on theCSI request field of the RAR grant may be configured to be performedbased on i) a nearest subframe which corresponds to a previous timingincluding a predefined value starting from a corresponding aperiodic CSIreporting timing and simultaneously satisfies the condition of apredefined valid CSI reference resource or ii) a subframe in which theCSI request field of the PAR grant for triggering correspondingaperiodic CSI reporting is received and simultaneously satisfies thecondition of the predefined valid CSI reference resource.

In this case, one of Embodiment 1-1 to Embodiment 1-5 may be applied tothe assumption about UL-DL configuration used to determine the locationof the valid CSI reference resource linked with corresponding aperiodicCSI reporting and the condition of the valid CSI reference resource. Fora detailed description, refer to the contents described in Embodiment1-1 to Embodiment 1-5.

For example, the location of the valid CSI reference resource linkedwith aperiodic CSI reporting may be configured to be determined inconsideration of only i) DL subframes and/or special subframes (e.g.,DwPTS) of UL-DL configuration of an SIB, ii) DL subframes and/or specialsubframes (e.g., DwPTS) of UL-DL configuration of a predefined referenceUL HARQ timeline, iii) DL subframes and/or special subframes (e.g.,DwPTS) of UL-DL configuration of a predefined reference DL HARQtimeline, iv) DL subframes and/or special subframes (e.g., DwPTS) of a(predefined) static resource set, or v) DL subframes and/or specialsubframes (e.g., DwPTS) of a duration during which resource usage isdetermined from a latest successfully received reconfiguration message.

Embodiment 1-16

According to the present invention, one of Embodiment 1-6 to Embodiment1-9 may be applied. For example, if the location of the valid CSIreference resource linked with aperiodic CSI reporting based on the CSIrequest field of the RAR grant belongs to a duration during whichresource usage is determined from a reception failed reconfigurationmessage, i) corresponding aperiodic CSI reporting is omitted, ii)corresponding aperiodic CSI reporting is performed using a specificpredefined value (e.g., RI/PMI/CQI), iii) corresponding aperiodic CSIreporting is performed using a latest successfully reported aperiodicCSI value, iv) corresponding aperiodic CSI reporting is performed(re)using a valid CSI reference resource of latest successfullyperformed CSI reporting, or v) valid CSI reference resources areregarded as being absent in a duration during which resource usage isdetermined from the reception failed reconfiguration message.

Embodiment 1-17

According to the present invention, aperiodic CSI reporting based on theCSI request field of the RAR grant may be configured to be performedbased on a subframe which corresponds to a timing prior to a predefinedvalue starting from a corresponding aperiodic CSI reporting timing andsimultaneously satisfies the condition of a predefined valid CSIreference resource.

In addition, in Embodiment 1-17, when a subframe prior to a predefinedvalue from the aperiodic CSI reporting timing does not satisfies thecondition of the (predefined) valid CSI reference resource,corresponding aperiodic CSI reporting may be configured to be omitted.

In this case, the assumption about UL-DL configuration used to determinethe location of the valid CSI reference resource linked withcorresponding aperiodic CSI reporting and the condition of the valid CSIreference resource may conform to one of Embodiment 1-1 to Embodiment1-5. For a detailed description, refer to the contents described inEmbodiment 1-1 to Embodiment 1-5.

Specifically, (the location of) the valid CSI reference resource linkedwith corresponding aperiodic CSI reporting may be determined inconsideration of only i) DL subframes and/or special subframes (e.g.,DwPTS) of UL-DL configuration of an SIB, ii) DL subframes and/or specialsubframes (e.g., DwPTS) of UL-DL configuration of a predefined referenceUL HARQ timeline, iii) DL subframes and/or special subframes (e.g.,DwPTS) of UL-DL configuration of a predefined reference DL HARQtimeline, iv) DL subframes and/or special subframes (e.g., DwPTS) of a(predefined) static resource set, or v) DL subframes and/or specialsubframes (e.g., DwPTS) of a duration during which resource usage isdetermined from a latest successfully received reconfiguration message.

Embodiment 1-18

In the present invention, at least one of Embodiments 1-15 to 1-17 ofthe present invention may be configured to be limitedly applied onlywhen aperiodic CSI reporting based on the CSI request field of the RARgrant corresponds to i) some cases of FIG. 9 (i.e., some of Cases A, B,C, and D) or ii) all cases of FIG. 9 (i.e., Case A, Case B, Case C, andCase D).

Second Embodiment

According to the second embodiment of the present invention, when thelocation of the valid CSI reference resource linked with CSI reportingof a specific timing is determined/detected based on predefinedconfigurations/rules, such a location determination/detection operationmay be configured to be performed only in a predefined time window. Forexample, when the location of the valid CSI reference resource linkedwith CSI reporting of a specific timing is determined/detected based onpredefined configurations/rules based on at least one of i)configuration for determining the valid CSI reference resource linkedwith CSI reporting, ii) configuration about a condition that should besatisfied to be considered as a valid CSI reference resource, and iii)configuration about an assumption about a UL-DL configuration (orresource usage configuration information) used to determine the locationof the valid CSI reference resource, such determination/detection may beconfigured to be performed in the predefined time window.

The above method may also be used to prevent inaccurate (or outdated)CSI reporting from being performed when the location of the valid CSIreference resource of unlicensed band related CSI reporting (of anunlicensed band) performed at a specific timing is set to a very oldtiming in the case in which an LTE system (re)uses a specific channel(e.g., an unlicensed band) of a Wi-Fi band by occupying the channelaperiodically (or with an irregular (transmission opportunity (TxOP))length) (on a sensing basis). For example, the unlicensed band relatedvalid CSI reference resource may be configured to be limitedly presentonly in a sensing based TxOP duration (e.g., DL subframe) and a UE maydetect the valid CSI reference resource in the corresponding duration.

Additionally, the above method may be extended to a non-fallback mode aswell as a fallback mode.

For example, a start point of the time window (hereinafter, “TW_START”)may be set to one of i) a CSI reporting timing, ii) a subframe prior toa predefined value (e.g., 4 ms or 5 ms) starting from the CSI reportingtiming, iii) a subframe in which a CSI request filed for triggering CSIreporting is received, iv) a subframe which corresponds to a timingprior to the predefined value starting from the CSI reporting timing andsimultaneously satisfies the condition of the predefined valid CSIreference resource, v) a nearest subframe which corresponds to aprevious timing including the predefined value starting from the CSIreporting timing and simultaneously satisfies the condition of thepredefined valid CSI reference resource, and vi) a subframe in which theCSI request field for triggering CSI reporting is received andsimultaneously the condition of the predefined valid CSI referenceresource is satisfied.

In addition, the size of the time window (hereinafter, “TW_SIZE”)determines a (total) duration for detecting/deriving the location of thevalid CSI reference resource linked with CSI reporting of a specifictiming from a predefined TW_START. Therefore, the location of the validCSI reference resource of a specific timing is detected/derived within a“duration from TW_START to TW_START-TW_SIZE” according to TW_START andTW_SIZE.

An eNB may be configured to inform a UE of information about TW_STARTand/or information about TW_SIZE through a predefined signal (e.g., aphysical layer signal or a higher layer signal). Alternatively, the eNBmay cause the UE to implicitly discern TW_START and/or TW_SIZE based ona predefined configuration/rule (e.g., TW_SIZE may be set to beimplicitly defined as a duration from TW_START to the first subframe ofa nearest previous radio frame).

Third Embodiment

At least one method/embodiment/configuration disclosed in the firstembodiment or the second embodiment of the present invention may beconfigured to be limitedly configured to partial predefined cases orpartial parameters. According to the third embodiment, the case in whichat least one method/embodiment/configuration disclosed in the first orsecond embodiment is applied is as follows.

The embodiments of the present invention may be configured to belimitedly applied only to the case in which a specific CSI reportingmethod (e.g., periodic CSI reporting or aperiodic CSI reporting) isconfigured or triggered.

The embodiments of the present invention may be configured to belimitedly applied only to the case in which a specific CSI reportingmode (e.g., a PUCCH reporting mode corresponding to periodic CSIreporting or a PUSCH reporting mode corresponding to aperiodic CSIreporting) is configured. In this case, the PUCCH reporting mode may be,for example, Mode 1-0, Mode 1-1, Mode 2-0, or Mode 2-1 and the PUSCHreporting mode may be, for example, Mode 1-2, Mode 2-0, Mode 2-2, Mode3-0, or Mode 3-1.

The embodiments of the present invention may be configured to belimitedly applied only to the case in which the condition of the validCSI reference resource is set to DL subframes and/or special subframes(e.g., DwPTS) rather than an MBSFN subframe.

The embodiments of the present invention may be configured to belimitedly applied only to the case in which a specific TM is configuredand/or a specific special subframe configuration is designated.

The embodiments of the present invention may be configured to belimitedly applied depending on whether a predefined reference signal(e.g., a CRS or a CSI-RS) is transmitted in a DL subframe and/or aspecial subframe (e.g., DwPTS) of a flexible resource set. That is, theembodiments of the present invention may be limitedly applied dependingon whether a specific control channel (e.g., PDCCH) can be transmittedor a specific TM can be configured.

The embodiments of the present invention may be configured to belimitedly applied according to a configuration type of a TM applied tothe DL subframe and/or the special subframe (e.g., DwPTS) of theflexible resource set. For example, the embodiments of the presentinvention may be configured to be limitedly applied only to the case inwhich a TM (e.g., TM 4) requiring decoding of a CRS based DL datachannel (PDSCH) is configured.

The embodiments of the present invention may be configured to belimitedly applied only to the case in which a specific number of CSIprocesses is configured.

The embodiments of the present invention may be configured to belimitedly applied only to a specific system environment (e.g., an FDDsystem or a TDD system).

The embodiments of the present invention may be configured to belimitedly applied only to an RRC_CONNECTED mode or IDLE mode of the UE.

The embodiments of the present invention may be configured to belimitedly applied only to the case in which a dynamic change mode ofradio resource usage is configured.

The embodiments of the present invention may be configured to belimitedly applied only to the case in which the eNB is configured toreceive, from the UE, feedback as to whether the reconfiguration messagehas been successfully received.

The embodiments of the present invention may be configured to belimitedly applied only to a specific component carrier (CC) or aspecific cell (e.g., a PCell or an SCell) in which a dynamic change modeof radio resource usage is configured in an environment in which CA isapplied.

Although the above-described embodiments may be independentlyimplemented, they may be implemented as a combination/aggregate of oneor more embodiments.

The eNB may inform the UE of information about the above-describedrules/configurations/embodiments of the present invention or informationas to whether the rules/configurations/embodiments are applied through apredefined signal (e.g., a physical layer or higher layer signal).

In addition, the embodiments of the present invention may be extended toan independent CSI reporting configuration per resource set (e.g.,static (DL) resource set or flexible (DL) resource set) of a differentinterference characteristic, i.e., at least one of the cases in which i)a CSI reporting mode is defined, ii) a CSI reporting method is defined,and iii) a periodic CSI reporting related period and a subframe offsetparameter are defined. The CSI reporting mode includes, for example, aPUCCH reporting mode (i.e., Mode 1-0, Mode 1-1, Mode 2-0, Mode 2-1)corresponding periodic CSI reporting and a PUSCH reporting mode (i.e.,Mode 1-2, Mode 2-0, Mode 2-2, Mode 3-0, Mode 3-1) corresponding toaperiodic CSI reporting. The CSI reporting method may include, forexample, periodic CSI reporting or aperiodic CSI reporting. The case inwhich the periodic CSI reporting related period and the subframe offsetparameter are defined includes, for example, resource-specific CSImeasurement or restricted CSI measurement.

The condition of the valid CSI reference resource of CSI reportinglinked with a specific resource set according to an embodiment of thepresent invention i) may be (re)interpreted as/(re)restricted to DLsubframes and/or special subframes (e.g., DwPTS) of the specificresource set or ii) may be (re)interpreted as/(re)restricted tosubframes included in the specific resource set among DL subframesand/or special subframes (e.g., DwPTS) based on which an assumptionabout UL-DL configuration is made to determine the location of the validCSI reference resource.

The above-described embodiments of the present invention may be extendedeven to the case in which the LTE system (re)uses a specific channel(e.g., an unlicensed band) of a Wi-Fi band occupied aperiodically (orwith an irregular duration (TxOP) length (on a sensing basis)).

Fourth Embodiment

In the fourth embodiment of the present invention, a method ofefficiently estimating and transmitting CSI by the UE when usage of aradio resource is dynamically changed according to an overhead state ofa system. The CSI means periodic CSI (P-CSI) and/or aperiodic CSI(A-CSI). The embodiments of the present invention may be extended to thecase in which the P-CSI is transmitted through a UL control channel(PUCCH), the P-CSI is transmitted through piggybacking on a UL datachannel (PUSCH), and/or the A-CSI is transmitted through the UL datachannel (PUSCH).

Hereinafter, the embodiments of the present invention will be describedbased on a 3GPP LTE system for convenience of description. However, therange of a system to which the present invention is applied may beextended to other systems in addition to the 3GPP LTE system. Theembodiments of the present invention may be extended to the case inwhich resource usage on a specific cell (or CC) is dynamically changedaccording to an overhead state of a system in an environment in which CAis applied. In addition, the embodiments of the present invention may beextended to the case in which usage of a radio resource is dynamicallychanged in a TDD system or an FDD system.

When the UE has not successfully received a reconfiguration messagetransmitted by the eNB, the UE may be configured to perform at least oneof i) a CSI measurement operation, ii) a PDCCH monitoring operation,iii) a PDSCH reception operation, and iv) a PUSCH transmissionoperation, based on UL-DL configuration of SIB type 1 (SIB1).

In the channel measurement operation, when the UE decodes explicit L1signaling of reconfiguration and detects valid UL-DL configuration, theUE measures CSI only in subframes indicated as DL subframes or specialsubframes by explicit L1 signaling of reconfiguration. If the UE doesnot detect L1 signaling for transmitting valid UL-DL configuration for aradio frame, the UE may measure the CSI only in subframes indicated asDL subframes or special subframes by SIB configuration. In the PDCCH orPDSCH reception operation, upon detecting L1 signaling for transmittingvalid UL-DL configuration for a radio frame, the UE monitors Inon-DRX DLsubframes or special subframes indicated by explicit L1 signaling. Uponnot detecting L1 signaling for transmitting valid UL-DL configurationfor the radio frame, the UE monitors the non-DRX DL subframes or specialsubframes for a PDCCH or an EPDCCH indicated by SIB-1 configuration.

Valid UL-DL configuration will now be described. DL HARQ referenceconfiguration may be selected from Rel-8 TDD UL-DL configurations {2, 4,5}. For the UE configured with TDD eIMTA (further enhancements to LTETDD for DL-UL interference management and traffic adaptation), a ULscheduling timing and a HARQ timing conform to UL-DL configurationsignaled through SIB2 . For valid UL HARQ reference configuration or DLHARQ reference configuration, the UE may regard a UL subframe or aspecial subframe in DL HARQ reference configuration as not beingdynamically used as a DL subframe or may regard a DL subframe or aspecial subframe in UL HARQ reference configuration as not beingdynamically used as a UL subframe.

UL grant validation will now be described. In a fallback mode, uponreceiving a UL grant corresponding to at least one UL subframe per SIB1not included in a set of UL subframes per DL HARQ referenceconfiguration, the UE may determine that the UL grant is valid controlinformation (valid grant). However, upon receiving NACK in a PHICHtriggering PUSCH transmission in a UL subframe per SIB1 which is notincluded in a set of UL subframes per DL HARQ reference configuration,the UE transmits a PUSCH. SRS transmission validation will now bedescribed. For type 1 STS, determination of a transmission scheduledsubframe of type 1 SRS when triggered is performed based on SIB1. Forboth type 0 SRS and type 1 SRS, SRS transmission may be performed in aUL subframe or a UpPTS based on SIB1.

That is, the above-described operations of i) to iv) are referred to asa “fallback operation” (or “fallback mode”). Through the fallbackoperation, the eNB may minimize i) damage of interference generated froma UE which has not successfully received a reconfiguration message(e.g., false detection of PDCCH/EPDCCH) on communication between anotherUE and an eNB (or a legacy UE and an eNB) or ii) malfunction of a UEwhich has not successfully received the reconfiguration message (e.g.,DL HARQ buffer corruption).

A method of performing a separate CSI-IM operation for interferencehaving different characteristics will now be described focusing on amethod of configuring a plurality of CSI measurement subframe sets(CSI-IM option #A).

For example, a serving cell may configure a resource-restricted CSImeasurement operation or a resource-specific CSI measurement operationin consideration of interference having different characteristicsreceived from a neighbor cell (e.g., a dominant interfering cell)performing a dynamic change operation of radio resource usage withrespect to a UE (eIMTA UE). Whether the resource-restricted CSImeasurement operation is applied is configured in the unit of a CSIprocess or a cell. The resource-restricted CSI measurement operation isimplemented by signaling/configuring (a maximum of) two CSI measurementsubframe sets in (one) CSI process or cell. The CSI measurement subframesets may be commonly assumed/configured/signaled or differentlyconfigured/signaled between CSI processes or between cells.

Additionally, for the UE (eIMTA UE), if two CSI measurement subframesets are configured for the resource-restricted CSI measurementoperation, two CSI-IM resources in one CSI process (i.e., having one(non-zero power) CSI-RS resource) may be signaled (i.e., refer to Table7) and each CSI-IM resource may be configured to be linked with anindividual CSI measurement subframe set. The above methods may beinterpreted such that it is assumed that minimum capability forconfiguring the number of CSI processes of the UE in which a dynamicchange mode of radio resource usage (eIMTA mode) can be configured is 1.Further, methods described in Table 7 (i.e., Option #1, Option #2, andOption #3) may be individually applied or may be applied in the form ofa combination thereof.

TABLE 7 CSI-IM configuration in TM 10 In TM10, in order to supportmultiple CSI measurement of a UE with single CSI process, multipleCSI-IM configurations can be considered. In other words, CSI-IMresources can be configured for each measurement subframe set, e.g.CSI-IM0 for static subframe set and CSI-IM1 for flexible subframe set.Then, a UE can make separate CSIs using 1 CSI-RS configuration and 2CSI-IM configurations, and the two-set CSI can be measured and reportedin TDD eMTA with TM 10 in a framework common to the other TMs. One mayclaim that one CSI process with two CSI-IM configuration (case 1) isequivalent to two CSI processes (case 2) in the sense that UE anywaymeasures end reports two different CSI, but there exist substantialdifference depending on the details of CSI process handling. First, itis always guaranteed in case 1 that the two CSI share the same NZPCSI-RS so that a UE does not need to be equipped with multiple channelmeasurement for CSI report, especially when the UE is capable ofhandling only one CSI process. Second, unless specified in the standard,the network is always able to configure two CSI subframe sets for eachCSI process, so in case 2, the maximum CSI to be supported for the UEcan increase to 4. Thus, without re-defining the CoMP UE capability andthe configurability of CSI measurement subframe set, supporting multipleCSI in TDD eIMTA by configuring multiple CSI processes requiresadditional implementation complexity which is beyond what the currentsingle- process-capable UE can support Another problem to solve forsupporting separate CSI measurements is the restriction of CSI-IMconfigurations where all CSI-IM resources must be covered by one ZPCSI-PS configuration. Because ZP CSI-RS configuration has a periodidtyof multiple of 5 ms, in most cases, only one interference condition(e.g. static SF or flexible SF) can be measured in TDD eIMTA. So, therestriction made in Rel-11 CoMP WI needs to be modified in Rel-12 TDDeIMTA. One way would be to maintain the restriction in the subframeswhere legacy UEs, including Rel-11 UEs, can expect CSI-IM configurationso that the existing restriction is still valid from their viewpoint.This implies that CSI-IMs configured on DL subframes indicated by SIB1should be coverable by a ZP CSI-RS configuration while CSI-IMsconfigured on the other subframes are not subject to this restriction.Consequently, the specified UE assumption can be changed acrossspecification releases in a smooth manner. [Option #1] Up to two CSI-IMconfigurations can be configured for a UE with single CSI process. Eachsubframe set can have own CSI-IM configuration. [Option #2] Therestriction of CSI-IM configurations where all CSI-IM resources must becovered by one ZP CSI-RS configuration can be removed on flexiblesubframes. [Option #3] Minimum UE capability on the number of CSIprocesses for TDD eIMTA is one.

For convenience of description, the two CSI measurement subframe setsare referred to as “CSI Measurement SF Set 0 (i.e., C_(CSI,0))”, and“CSI Measurement SF Set #1 (i.e., C_(CSI,1))”, respectively. In thiscase, CSI Measurement SF Set #0 (i.e., C_(CSI,0)) may be configured inconsideration of a subframe set in which interference of a relativelystatic characteristic (or interference of a fixed characteristic) isreceived from a neighbor cell performing a dynamic change operation ofradio resource usage and CSI Measurement SF Set #1 (i.e., C_(CSI,1)) maybe configured in consideration of a subframe set in which interferenceof a relatively variant characteristic is received.

Specifically, the subframe set in which a neighbor cell performing thedynamic change operation of radio resource usage generates interferenceof a relatively static characteristic (or fixed characteristic) may be asubframe set that the neighbor cell uses for static usage (or fixedusage) (e.g., at least one of a DL subframe/special subframe set of SIB1based UL-DL configuration, a DL subframe/special subframe set of UL HARQreference configuration, and a UL subframe/special subframe set of DLHARQ reference configuration).

Meanwhile, the subframe set in which a neighbor cell generatesinterference of a relatively variant characteristic may be a subframeset in which the neighbor cell performs usage change. For example, thesubframe set may be UL subframes/special subframes except for ULsubframes/special subframes of DL HARQ reference configuration among ULsubframes/special subframes of SIB1 based UL-DL configuration or DLsubframes/special subframes of UL HARQ reference configuration. Asanother example, the subframe set in which the neighbor cell generatesinterference of a relatively variant characteristic may be DLsubframes/special subframes except for DL subframes/special subframes ofSIB1 based UL-DL configuration or DL subframes/special subframes of ULHARQ reference configuration among DL subframes/special subframes of DLHARQ reference configuration.

CSI Measurement SF Set #0 (i.e., C_(CSI,0)) and CSI Measurement SF Set#1 (i.e., C_(CSI,1)) may be configured in consideration of a subframeset for static or fixed usage and a subframe set in which the servingcell performs usage change, respectively.

Hereinafter, a separate CSI/IM operation for interference havingdifferent characteristics will be described focusing on a method ofconfiguring a plurality of CSI processes (CSI/IM Option #B).

For example, a serving cell may be configured such that the UE (eIMTAUE) performs at least one of a separate CSI measurement operation, aninterference estimation operation, and an interference averagingoperation with respect to interference having different characteristicsreceived from a neighbor cell performing a dynamic change operation ofradio resource usage in a form different from that of Table 7.Specifically, if the UE (eIMTA/TM 10 UE) informs the eNB that the UE iscapable of supporting a maximum of P CSI processes through “CapabilitySignaling”, the UE may configure a maximum of N*P (although N may be setto a positive integer equal to or greater than 2, N will be assumed tobe 2 for convenience of description) CSI processes from the eNB.

If ‘N=2’ and a total of 2*P CSI processes is configured for the UE(eIMTA UE) by the eNB, a combination of one specific non-zero powerCSI-RS resource and one CSI-IM resource may be configured in the samemanner as legacy Rel-11 CSI processes, limited only to a maximum of PCSI processes (e.g., from the first CSI process (i.e., CSI process index#1) to the P-th CSI process (i.e., CSI process index #P)) among a(maximum of) 2*P CSI processes. The other CSI processes (e.g., from the(P+1)-th CSI process (i.e., CSI process index #(P+1) to the (2*P)-th CSIprocess (i.e., CSI process index #(2*P)) may be configured to use someinformation (e.g., non-zero power CSI-RS resource configurationinformation) by pairing with one of the P CSI processes (e.g., from thefirst CSI process (i.e., CSI process index #1) to the P-th CSI process(i.e., CSI process index #P) in which a combination of one specificnon-zero power CSI-RS resource and one CSI-IM resource is configured inthe same manner as the legacy Rel-11 CSI processes according topredefined rule/configuration/signaling information (i.e., one CSIprocess is not paired with a plurality of CSI processes and one CSIprocess is mapped to one CSI process without overlap).

TABLE 8 Aperiodic CSI in TM10 for eIMTA A UE capable of TM10 and eIMTAshall support the configuration of 2 CSI processes   If a UE indicatedthat it supports 1 CSI process for TM10, and the UE is configured witheIMTA   and 2 TM10 CSI processes, the UE should not expect:     Theconfiguration of different NZP CSI-RS resources for the 2 CSI processes(i.e. CSI-RS-     ConfigNZPId should be the same)     The configurationof RI-reference CSI process (ri-Ref-CSI-ProcessId)     (Theconfiguration of CSI measurement subframe sets)     (The simultaneousA-CSI reports of two CSI processes by a single A-CSI trigger)     [Note]The above restrictions should be specified in order for the two CSIprocesses to     be equivalent to a single CSI process configured withtwo CSI measurement subframe     sets in terms of UE complexity.   (If aUE indicated that it supports 1 CSI process for TM10 and the UE is notconfigured with   eIMTA, the UE should not expect the configuration ofmore than 1 CSI process.)   (As in Rel-11 specifications, when more thanone CSI process is configured, 2-bit CSI request   field will be used inDCI format 0 (in UE SS) and DCI format 4.)

Table 8 shows an example of using non-zero power CSI-RS resourceconfiguration information after the other CSI process (e.g., the secondCSI process (i.e., CSI process index #2)) is paired with one CSI process(e.g., the first CSI process (i.e., CSI process index #1)) in which acombination of one specific non-zero power CSI-RS resource and oneCSI-IM resource is configured in the same manner as the legacy Rel-11CSI processes according to predefined rule/configuration/signalinginformation in a situation in which ‘P=1 and N=2’ and a total of two CSIprocesses is configured for the UE (eIMTA UE) by the eNB.

In this case, in the other CSI process (e.g., second CSI process (i.e.,CSI process index #2)), a CSI-IM resource different from one CSI process(e.g., the first CSI process (i.e., CSI process index #1)) in which acombination of one specific non-zero power CSI-RS resource and oneCSI-IM resource is configured in the same manner as the legacy Rel-11CSI processes is configured. The CSI processes are used to perform theseparate CSI measurement operation, interference estimation operation,or interference averaging operation with respect to subframe sets of(implicitly) different interference characteristics. In other words, theCSI processes perform the same role as CSI Measurement SF Set #0 (i.e.,C_(CSI,0)) and CSI Measurement SF Set #1 (i.e., C_(CSI,1)) describedabove.

As another example, pair mapping between 2*P CSI processes (i.e., fromCSI process index #1 to CSI process index #2*P) may be performedaccording to predefined configuration. As a detailed example, specificCSI process index #k (where k ∈{1, 2 , . . . , P}) may be configured toperform pair mapping with CSI process index #(k+P) (i.e., specific CSIprocess index #k (where k ∈{(P+1),(P+2), . . . , 2*P}) may bepair-mapped to CSI process index #(k mod P) (where “k mod P” is aremainder obtained by dividing k by P) or specific CSI process index #k(where k ∈{1, 2 , . . . , P}) may be configured to perform pair mappingwith CSI process index #(k+O_(offset)) (where O_(offset) may be set to apositive integer other than 0). In this case, if the eNBsignals/configures a total number of CSI processes by a value or an oddnumber less than 2*P for the UE (eIMTA UE), the UE may have CSIprocesses to which pair mapping is not actually applied and thecorresponding CSI processes may be independently used (e.g., for CoMP).

Hereinafter, a method of efficiently reporting CSI when the UE performsa fallback operation will be proposed based on the above description.The embodiments of the present invention may be configured to belimitedly applied to a P-CSI reporting operation or an A-CSI reportingoperation or may be configured to be applied to both the P-CSI reportingoperation and the A-CSI reporting operation.

The following embodiments may be configured to be limitedly applied onlyto at least one of a CSI measurement operation, a PDCCH monitoringoperation, a PDSCH reception operation, and a PUSCH (re)transmissionoperation, based on UL-DL configuration of SIB1 in a fallback mode,i.e., when a reconfiguration message has not been successfully received.

This is because, in a duration during which the fallback mode isperformed, the UE performs the CSI measurement operation inconsideration of only DL subframes and/or special subframes of SIB1based UL-DL configuration and, in this case, there is a high probabilitythat the DL subframes and/or the special subframes of SIB1 based UL-DLconfiguration are set to one specific CSI measurement subframe set(i.e., a subframe set in which interference of a relatively static (orfixed) characteristic is received from a neighbor cell or a subframe setused for static usage (or fixed usage) by a serving cell (hereinafter,CSI measurement subframe set #0 (C_(CSI,0)))).

In other words, in a duration during which the fallback mode isperformed, only CSI reference resources for (P/A−) CSI reporting relatedto one specific CSI measurement subframe set (i.e., CSI measurementsubframe set #0, C_(CSI,0)) are present and CSI reference resources for(P/A−) CSI reporting related to the other CSI measurement subframe set(i.e., a subframe set in which interference of a relatively variantcharacteristic is received from a neighbor cell or a subframe set inwhich a serving cell performs usage change (hereinafter CSI measurementsubframe set #1 (C_(CSI,1)))) are not present. Accordingly, a method ofefficiently processing (P/A−) CSI reporting related to the other CSImeasurement subframe set (i.e., CSI measurement subframe set #1(C_(CSI,1))) is needed and the embodiments of the present invention maybe applied to this case.

The embodiments of the present invention may be extended even to thecase in which UL-DL configuration (re)designated by a reconfigurationmessage is the same as SIB1 based UL-DL configuration. That is, if UL-DLconfiguration (re)designated by the reconfiguration message is the sameas SIB1 based UL-DL configuration, the problem in which CSI referenceresources for (P/A−) CSI reporting related to the other CSI measurementsubframe set (CSI measurement subframe set #1(C_(CSI,1))) are notpresent (i.e., in this case, the problem occurs regardless of a fallbackmode and a non-fallback mode) occurs equally.

Additionally, the embodiments of the present invention may be applied toboth the case in which at least one of a CSI measurement operation, aPDCCH monitoring operation, a PDSCH reception operation, and a PUSCH(re)transmission operation based on UL-DL configuration of SIB1 isperformed in a fallback mode, i.e., when the UE has not successfullyreceived the reconfiguration message and the case in which at least oneof a channel measurement operation, a PDCCH monitoring operation, aPDSCH reception operation, and a PUSCH (re)transmission operation isperformed based on a non-fallback mode, i.e., information about asuccessfully received reconfiguration message (i.e., reconfigured validUL-DL configuration information).

The following embodiments may be configured to be limitedly applied onlyto some cases (e.g., Table 7 or 8) in which at least one of the CSImeasurement operation, interference estimation operation, andinterference averaging operation with respect to interference of theabove-described different characteristics is performed or may beconfigured to be applied to all methods.

FIG. 10 is a diagram referred to in explaining a mode duration (e.g., afallback mode duration or a non-fallback mode duration) to which a CSIreporting timing of a specific UE (eIMTA UE) and/or a timing/location ofa valid reference resource (e.g., CSI reference resource) linked withcorresponding CSI reporting (e.g., a rule for determining thetiming/location of the valid reference resource linked with CSIreporting of a specific timing is defined in TS 36.213) belongs.

In FIG. 10(a), CSI reporting of a specific timing is performed in aduration during which a fallback mode operation is applied and atiming/location of a valid reference resource of corresponding CSIreporting is present in the duration during which the fallback modeoperation is applied. In FIG. 10(b), CSI reporting of a specific timingis performed in a duration during which a non-fallback mode operation isapplied and the timing/location of the valid reference resource ofcorresponding CSI reporting is present in a duration during which thefallback mode operation is applied. In FIG. 10(c), CSI reporting of aspecific timing is performed in a duration during which the fallbackmode operation is applied and the timing/location of the valid referenceresource of corresponding CSI reporting is present in a duration duringwhich the non-fallback mode operation is applied. It is assumed in FIG.10 that a duration during which the fallback mode is applied or aduration during which the non-fallback mode is applied is determinedbased on a dynamic reconfiguration period of radio resource usage.

The following embodiments may be configured to be limitedly applied onlyto some cases of FIG. 10 or may be configured to be applied to all casesof FIG. 10. Additionally, the following embodiments may be extended tothe case in which CSI reporting of a specific timing is performed in aduration during which the non-fallback mode operation is applied and thetiming/location of the valid reference resource of corresponding CSIreporting is present in a duration during which the non-fallback modeoperation is applied (e.g., the case in which UL-DL configuration(re)designated by the reconfiguration message is the same as SIB1 basedUL-DL configuration).

Embodiment 4-1

According to Embodiment 4-1 of the present invention, in at least one(i.e., some or all) of the cases of FIG. 10, the UE (eIMTA UE) may beconfigured (as an exceptional case) to omit at least one of an operationof reporting at least one of a CQI, a PMI, a precoding type indicator(PTI), and a rank indication (RI) of a predefined specific value and anoperation of reporting CQI information, PMI information, PTIinformation, and RI information.

For example, the CQI information (e.g., wideband CQI or subband CQI) mayreport (as an exceptional case) “out-of-range (OOR) value” (i.e., avalue corresponding to CQI index #0) and, thus, the eNB maydiscern/derive a fallback mode operation by the UE.

As another example, at least one of the RI information and joint-encodedPTI information may be configured (as an exceptional case) to report apredefined value (e.g., 1) or to report again at least one of the latestRI value and PTI information. As an example of the latter case, the UEmay be configured to report again at least one of the latestcalculated/reported RI value (and/or PTI information) based on a validreference resource located in a non-fallback mode duration and thelatest reported RI value (and/or PTI information) in the non-fallbackmode duration. The above-described methods enable reporting of incorrector invalid RI information, thereby preventing (re)occurrence of an errorin the CQI information, PMI information, or PTI information calculatedbased on the RI information.

As still another example, at least one of the CQI information, PMIinformation, PTI information, and RI information of a specific valuereported based on this embodiment may be configured to be transmittedthrough (as an exceptional case) a predefined or signaled resource(e.g., PUCCH/PUSCH resource).

As another example, in FIG. 10(a) to FIG. 10(c), the UE may omit (as anexceptional case) reporting of information other than (particularly,P-CSI or A-CSI related) RI information, CQI information, PMIinformation, and PTI information having a specific value according to apredefined rule/configuration.

As another example, in FIG. 10(a) to FIG. 10(c), (8-TX antenna) PTIinformation may be reported/configured (as an exceptional case) with apredefined value (e.g., ‘PTI=0’ or ‘PTI=1’) and an attribute of at leastone of (future reported) W1, W2, and CQI may be determined based on thePTI information. Generally, if the PTI information is set to 0, widebandW1 and wideband W2/CQI are reported and, if the PTI information is setto 1, wideband W2 and subband W2/CQI/L-bit subband indicator arereported.

As another example, in FIG. 10(a) to FIG. 10(c), reporting (i.e.,subband attribute based reporting) other than wideband attribute basedreporting among reporting related to CQI/PMI information may beconfigured (as an exceptional case) to be omitted, reporting (i.e.,wideband attribute based reporting) other than subband attribute basedreporting may be configured to be omitted, or reporting based on allattributes (i.e., wideband/subband attribute based reporting) may beconfigured to be omitted.

As another example, according to this embodiment, the same rule may beapplied even to the case in which a valid reference resource forspecific CSI reporting of (a specific timing) is not present in apreconfigured or signaled duration (window of the valid CSI referenceresource) (i.e., when the valid reference resource is out of a lowerbound of a predetermined duration).

Embodiment 4-2

According to Embodiment 4-2 of the present invention, Embodiment 4-1 maybe limitedly applied only to a method of performing the above-describedseparate CSI measurement operation, interference estimation operation,or interference averaging operation, for interference having differentcharacteristics, according to a predefined rule or signaled information.That is, in Table 7, Embodiment 4-1 may be limited applied only to a CSIreporting operation (e.g., P-CSI reporting operation and/or A-CSIreporting operation) related to a specific CSI measurement subframe setor a specific CSI measurement subframe set index.

For example, a CSI measurement subframe set to which Embodiment 4-1 isapplied may be defined (implicitly or based on signaling) as a CSImeasurement subframe set linked with a subframe set in whichinterference of a relatively variant characteristic is received from aneighbor cell (or a subframe set in which a serving cell performs changeusage) or may be defined as a specific predefined or signaled (fixed)CSI measurement subframe set. Alternatively, the CSI measurementsubframe set index to which Embodiment 4-1 is applied may be defined(implicitly or based on signaling) as a CSI measurement subframe setindex (i.e., CSI measurement subframe set index #1 or C_(CSI,1)) linkedwith a subframe set in which interference of a relatively variantcharacteristic is received from a neighbor cell (or a subframe set inwhich a serving cell performs change usage) or may be defined as aspecific predefined or signaled (fixed) CSI measurement subframe setindex (i.e., CSI measurement subframe set index #1 or C_(CSI,1)).

As another example, the CSI measurement subframe set to which Embodiment4-1 is applied may be defined (implicitly or based on signaling) as aCSI measurement subframe set linked with a subframe set in whichinterference of a relatively static (or fixed) characteristic isreceived from a neighbor cell (or a subframe set that a serving celluses for static (or fixed) usage) or may be defined as a specificpredefined (or signaled) (fixed) CSI measurement subframe set.Alternatively, the CSI measurement subframe set index to whichEmbodiment 4-1 is applied may be defined (implicitly or based onsignaling) as a CSI measurement subframe set index (i.e., CSImeasurement subframe set index #0 (i.e., C_(CSI,0))) linked with asubframe set in which interference of a relatively static (or fixed)characteristic is received from a neighbor cell (or a subframe set thata serving cell uses for static (or fixed) usage) or may be defined as aspecific predefined (or signaled) (fixed) CSI measurement subframe setindex (i.e., CSI measurement subframe set index #0 or C_(CSI,0)).

Additionally, the CSI measurement subframe set or the CSI measurementsubframe set index to which Embodiment 4-1 is applied may be defined(implicitly or based on signaling) as all CSI measurement subframe setsor CSI measurement subframe set indexes (i.e., CSI measurement subframeset index #0 (C_(CSI,0)) and CSI measurement subframe set index #1(C_(CSI,1))).

Embodiment 4-3

According to Embodiment 4-3, Embodiment 4-1 may be limitedly appliedonly to a method of performing the above-described separate CSImeasurement operation, interference estimation operation, orinterference averaging operation, for interference having differentcharacteristics, according to a predefined rule (or signaledinformation). That is, Embodiment 4-1 may be configured to be limitedapplied only to a specific CSI process index related CSI reportingoperation (e.g., P-CSI reporting operation and/or A-CSI reportingoperation) in Table 8.

For example, a CSI process index to which Embodiment 4-1 is applied maybe defined (implicitly or based on signaling) as a CSI process indexwhich is used or configured to perform the separate CSI measurementoperation, interference estimation operation or interference averagingoperation, in a subframe set in which interference of a relativelyvariant characteristic is received from a neighbor cell (or a subframeset in which a serving cell performs usage change) or may be defined asa specific predefined (or signaled) (fixed) CSI process index.

As an example in which [proposed method #1] is applied to a specificpredefined (fixed) CSI process index, Embodiment 4-1 may be limitedlyapplied only to CSI processes (e.g., from CSI process index #(P+1) toCSI process index #(2*P)) which pair with one of P CSI processes (i.e.,one CSI process is not paired with a plurality of CSI processes and oneCSI process is mapped to one CSI process without overlap) and use someinformation (e.g., non-zero power CSI-RS resource configurationinformation), other than P CSI processes (e.g., from CSI process index#1 to CSI process index #P) in which a combination of one specificnon-zero power CSI-RS resource and one CSI-IM resource is configured inthe same manner as legacy Rel-11 CSI processes among 2*P CSI processes(i.e., ‘N=2’).

As another example, a CSI process index to which Embodiment 4-1 isapplied may be defined as a CSI process index (implicitly or based onsignaling) which is configured to perform the separate CSI measurementoperation, interference estimation operation, or interference averagingoperation, in a subframe set in which interference of a relativelystatic (or fixed) characteristic is received from a neighbor cell (or asubframe set used for static usage (or fixed usage) by a serving cell)or may be defined as a specific predefined (or signaled) (fixed) CSIprocess index.

That is, as an example in which Embodiment 4-1 is applied to a specificpredefined (fixed) CSI process index, Embodiment 4-1 may be limitedlyapplied to P CSI processes (e.g., CSI process index #1 to CSI processindex #P) in which a combination of one specific non-zero power CSI-RSresource and one CSI-IM resource is configured in the same manner aslegacy Rel-11 CSI processes among 2*P CSI processes (i.e., the case inwhich ‘N=2’). That is, Embodiment 4-1 may be configured not to beapplied to the other CSI processes (e.g., from CSI process index #(P+1)to CSI process index #(2*P)) which pair with one of the P CSI processes(i.e., one CSI process is not paired with a plurality of CSI processesand one CSI process is mapped to one CSI process without overlap)according to a predefined rule (or signaling information) and use someinformation (e.g., non-zero power CSI-RS resource configurationinformation).

Additionally, the CSI process index to which Embodiment 4-1 is appliedmay be defined as all CSI process indexes (e.g., from CSI process index#1 to CSI process index #(2*P) when ‘N=2’) or may be defined as a totalnumber of CSI processes configured for the UE by the eNB) (implicitly orbased on signaling).

Embodiment 4-4

According to Embodiment 4-4 of the present invention, a lower bound of awindow in which valid CSI reference resource(s) related to CSI reportingof a specific timing (i.e., SF#N) can be present may be configured to bea timing at which a (predefined) PDCCH is transmitted, a timing whichincludes the (predefined) PDCCH transmission timing and is located afterthe (predefined) PDCCH transmission timing, or a timing which does notinclude the (predefined) PDCCH transmission timing and is located afterthe (predefined) PDCCH transmission timing.

For example, the (predefined) PDCCH transmission timing may be definedas a subframe in which a reconfiguration message (refer to Table 9) istransmitted or may be defined as a start point of a window in which thesame reconfiguration message (and in which a CSI reporting timing (i.e.,SF#N) is included) (in terms of the UE performing CSI reporting of aspecific timing (i.e., SF#N)) is transmitted. When the abovemethods/rules are applied, reporting of outdated CSI information causedby selecting the location (and/or timing) of a valid CSI referenceresource location related to CSI reporting of a specific timing (i.e.,SF#N) as a very old timing can be prevented. For example, a subframe inwhich the reconfiguration message is transmitted may be defined as“subframes satisfying (10·n_(f)+n−k)mod T=0 ” as in Table 9 and a windowin which the same reconfiguration message is transmitted may be definedas “radio frames {m·T/10,m·T/10+1,. . . , (m+1)·T/10−1} or{(m+1)·T/10,(m+1)·T/10+1,. . . , (m+2)·T/10−1}” as in Table 9.

TABLE 9 Details of signalling for TDD UL-DL reconfiguration The UE isconfigured to monitor the reconfiguration DCI in subframes satisfying(10 · n_(f) + n − k) modT = 0, where n is the subframe number within aradio frame, n_(f) is the radio frame number, T and k are defined in thefollowing table. The UL-DL configuration indicated by thereconfiguration DCI received in a subframe in radio frame (s) {m · T/10,m · T/10 + 1, . . . , (m + 1) · T/10 − 1}is valid for either {m · T/10,m · T/10 + 1, . . . , (m + 1) · T/10 − 1} (denoted as “Current”) or{(m + 1) · T/10, (m + 1) · T/10 + 1, . . . , (m + 2) · T/10 − 1}(denoted as “Next”) , as indicated by the following table. UE is notrequired to wake-up to monitor explicit reconfiguration DCI in DRX OFF.FFS whether to specify the following two UE behaviours: Behaviour 1: Ifa UE is configured to monitor in multiple subframes reconfiguration DCIsfor radio frames {m · T/10, m · T/10 + 1, . . . , (m + 1) · T/10 − 1},the UE may skip decoding the reconfiguration DCI for radio frames {m ·T/10, m · T/10 + 1, . . . , (m + 1) · T/10 − 1} if the UE hassuccessfully decoded at least one reconfiguration DCI for radio frames{m · T/10, m · T/10 + 1, . . . , (m + 1) · T/10 − 1}. Behaviour 2: If aUE is configured to monitor in multiple subframes reconfiguration DCIsfor radio frames {m · T/10, m · T/10 + 1, . . . , (m + 1) · T/10 − 1},the UE shall or may assume the same UL-DL configuration indicated by thereconfiguration DCIs for radio frames {m · T/10, m · T/10 + 1, . . . ,(m + 1) · T/10 − 1}. Periodicity T (ms) Offset k (ms) (0 ≦ k < T) Validduration 10 A X-bit bitmap to indicate a set of “Current” for the SIB-1DL/S subframe. Starting from reconfiguration DCI in the MSB to LSB, thebitmap subframe #0 corresponds to subframe #{[Xa, Xb, “Next” for the Xc,. . . ]}. The bit “1” indicates that UE reconfiguration DCI in the shallmonitor the reconfiguration DCI SIB1 DL/S subframes in the correspondingsubframe, and the other than subframe #0 bit “0” indicates otherwise. 20A Y-bit bitmap to indicate a set of [“Current” for the SIB-1 DL/Ssubframe. Starting from reconfiguration DCI in the MSB to LSB, thebitmap subframe #0 in the first corresponds to subframe #{[Ya, Yb, radioframe in the window, Yc, . . . ]}. The bit “1” indicates that UE ifsupported by the Y-bit shall monitor the reconfiguration DCI bitmap] inthe corresponding subframe, and the “Next” for the bit “0” indicatesotherwise. reconfiguration DCI in the SIB1 DL/S subframes other thansubframe #0 in the first radio frame in the window 40 A Z-bit bitmap toindicate a set of SIB- [“Current” for the 1 DL/S subframe. Starting fromthe reconfiguration DCI in MSB to LSB, the bitmap corresponds subframe#0 in the first to subframe #{[Za, Zb, Zc, . . . ]}. The radio frame inthe window, bit “1” indicates that UE shall monitor if supported by theZ-bit the reconfiguration DCI in the bitmap] corresponding subframe, andthe bit “Next” for the “0” indicates otherwise. reconfiguration DCI inthe SIB1 DL/S subframes other than subframe #0 in the first radio framein the window [80] A Q-bit bitmap to indicate a set of [“Current” forthe SIB-1 DL/S subframe. Starting from reconfiguration DCI in the MSB toLSB, the bitmap subframe #0 in the first corresponds to subframe #{[Qa,Qb, radio frame in the window, Qc, . . . ]}. The bit “1” indicates thatUE if supported by the Q-bit shall monitor the reconfiguration DCIbitmap] in the corresponding subframe, and the “Next” for the bit “0”indicates otherwise. reconfiguration DCI in the SIB1 DL/S subframesother than subframe #0 in the first radio frame in the window Confirmthe working assumption that the periodicity of the reconfigurationsignals includes at least 10 ms, 20 ms, 40 ms Check if the workingassumption of 80 ms periodicity can be confirmed in RAN1#76 For 10 msperiodicity, the value of X is at least 4 and subframes #{[Xa, Xb, Xc, .. . ]} includes at least subframes #{0, 1, 5, 6} The exact value of Xand subframes #{[Xa, Xb, Xc, . . . ]} is to be agreed in RAN1#76 For 20ms periodicity, the value of Y is at least 4 and subframes #{[Ya, Yb,Yc, . . . ]} includes at least subframes #{0, 1, 5, 6} in the 2nd radioframe in the window The exact value of Y and subframes #{[Ya, Yb, Yc, .. . ]} is to be agreed in RAN1#76 For 40 ms periodicity, the value of Zis at least 4 and subframes #{[Za, Zb, Zc, . . . ]} includes at leastsubframes #{0, 1, 5, 6} in the 4th radio frame in the window The exactvalue of Z and subframes #{[Za, Zb, Zc, . . . ]} is to be agreed inRAN1#76 For 80 ms periodicity, if confirmed in RAN1#76, the value of Qis at least 4 and subframes #{[Qa, Qb, Qc, . . . ]} includes at leastsubframes #{0, 1, 5, 6} in the 8th radio frame in the window The exactvalue of Q and subframes #{[Qa, Qb, Qc, . . . ]} is to be agreed inRAN1#76, if 80 ms periodicity is confirmed UE shall not be configured tomonitor reconfiguration DCI in non-SIB-1 DL/S subframes The size of DCIthat carries reconfiguration bits is aligned to DCI format 1C. If UEdoes not detect L1 signaling conveying a valid UL-DL configuration for aradio frame, UE shall monitor the non-DRX DL subframes or specialsubframes for PDCCH or EPDCCH as indicated by SIB-1 configuration 80 msperiodicity for the reconfiguration signaling is supported. The numberof eIMTA-RNTI configured for a UE is 1. The eIMTA-RNTI isUE-specifically configured via RRC Different UEs may be configureddifferent eIMTA-RNTIs The set of subframes that UE monitors for theexplicit reconfiguration DCI is UE-specifically configured via RRC Themapping between a reconfiguration index and a cell is UE-specificallyconfigured via RRC The explicit reconfiguration DCI only carriesinformation for explicit reconfiguration The set of subframes that a UEis possibly configured to monitor the reconfiguration signalling arebased on: For 10 ms periodicity, the set of subframes are the DLsubframes and special subframes per SIB1 For 20 ms periodicity, the setof subframes are the DL subframes and special subframes per SIB1 in the2nd radio frame in the window For 40 ms periodicity, the set ofsubframes are the DL subframes and special subframes per SIB1 in the 4thradio frame in the window For 80 ms periodicity, the set of subframesare the DL subframes and special subframes per SIB1 in the 8th radioframe in the window The following is to be captured in thespecification: If a UE is configured to monitor in multiple subframesreconfiguration DCIs for radio frames {m · T/10, m · T/10 + 1, . . . ,(m + 1) · T/10 − 1}, the UE may assume the same UL-DL configurationindicated by the reconfiguration DCIs for radio frames {m · T/10, m ·T/10 + 1, . . . , (m + 1) · T/10 − 1}. The same UL-DL configuration hererefers to any cell configured for the UE with eIMTA-enabled UE isrequired to monitor all subframes to carry reconfiguration DCI (s) forradio frames {m · T/10, m · T/10 + 1, . . . , (m + 1) · T/10 − 1} atleast until one valid UL-DL configuration for radio frames {m · T/10, m· T/10 + 1, . . . , (m + 1) · T/10 − 1} is detected.

In addition, an upper bound of a window at which valid CSI referenceresource(s) related to CSI reporting of a specific timing (i.e., SF#N)can be present may be set to SF#(N-4) (or a timing at which an A-CSItriggering message is received in the case of A-CSI reporting) through apredefined rule (or predefined signaling).

The present embodiment may be configured to be limitedly applied only toa specific CSI measurement subframe set or a specific CSI measurementsubframe set index or to be applied to all CSI reporting operations. Forexample, the present embodiment may be configured to be limitedlyapplied to a subframe set in which interference of a relatively variantcharacteristic is received from a neighbor cell (or a subframe set inwhich the serving cell performs usage change), i.e., to a P-CSIreporting operation or a A-CSI reporting operation related to CSImeasurement subframe set index #1 (i.e., C_(CSI,1)).

Embodiment 4-4 may be configured to be limitedly applied only to afallback mode or both to the fallback mode and a non-fallback mode.

FIG. 11 is a diagram referred to in explaining the case in whichEmbodiment 4-4 is applied. In FIG. 11, a lower bound of a window inwhich valid CSI reference resource(s) related to CSI reporting of aspecific timing (i.e., SF#N) may be assumed as a start point of a windowduring which the CSI reporting timing (i.e., SF#N) is included and thesame reconfiguration message is transmitted. An upper bound of a windowin which CSI reporting related valid CSI reference resource(s) of aspecific timing (i.e., SF#N) can be present may be assumed as SF#(N-4)through predefined configuration/rule/signaling.

Embodiment 4-5

At least one of Embodiment 4-1, Embodiment 4-3, and Embodiment 4-4 ofthe present invention may be configured to be limitedly applied only toa P-CSI reporting operation (or an A-CSI reporting operation) related tothe specific CSI measurement subframe set or the specific CSImeasurement subframe set index described in Embodiment 4-2 or may beconfigured to be applied to all of the CSI reporting operations.

At least one of Embodiment 4-1, Embodiment 4-2, and Embodiment 4-4 ofthe present invention may be configured to be limitedly applied only tothe P-CSI reporting operation (or the A-CSI reporting operation) relatedto the specific CSI process index described in Embodiment 4-3 or may beconfigured to be applied to all of the CSI reporting operations.

Embodiment 4-6

At least one of Embodiment 4-1 to Embodiment 4-5 of the presentinvention may be configured to be limitedly applied only to a specificcase of FIG. 10 (e.g., FIG. 10(a), FIG. 10(b), or FIG. 10(c)), may beconfigured to be limitedly applied only to a combination of some cases(e.g., a combination of FIG. 10(a) and FIG. 10(b) or a combination ofFIG. 10(a) and FIG. 10(c)), or may be configured to be applied to allcases.

At least one of Embodiment 4-1 to Embodiment 4-5 of the presentinvention may be configured to be limitedly applied only to a specificTM (e.g., Embodiment 4-3 is limitedly applied only to TM 10 orEmbodiment 4-2 is limitedly applied only to TM 9/TM 10 (or TM 1 to TM10) or may be configured to be applied to all TMs.

Furthermore, the above-described embodiments may be configured to belimitedly applied only to the case in which a dynamic change (eIMTA)mode of radio resource usage is configured, the case in which a specificTM is configured, or the case in which specific UL-DL configuration is(re)configured.

It is apparent that examples/configurations/rules of the above-describedembodiments may be regarded as proposed schemes for carrying out thepresent invention. In addition, although the above-described embodimentsmay be independently implemented, they may be implemented as acombination/aggregate of one or more embodiments.

Information about the embodiments/configurations/rules of the presentinvention or information as to whether theembodiments/configurations/rules of the present invention are appliedmay be signaled to the UE by the eNB through a predefined signal (e.g.,physical layer or higher layer signal).

The above-described embodiments may be configured to be limitedlyapplied only to a predefined (or signaled) specific CSI feedbackmode/type (e.g., a feedback mode/type performed through a PUSCH or afeedback mode/type performed through a PUCCH) or may be configured to belimitedly applied only to the case in which a PMI/RI reporting operationis configured or the PMI/RI reporting operation is disabled.Alternatively, the present invention may be applied regardless ofwhether the PMI/RI reporting operation is configured.

The above-described embodiments of the present invention may beconfigured to be limitedly applied only to at least one (i.e., some orall) of CQI information, PMI information, PTI information, and RIinformation reporting operations.

FIG. 12 illustrates a BS and a UE that are applicable to an embodimentof the present invention.

If a wireless communication system includes a relay, communication in abackhaul link is performed between the BS and the relay andcommunication in an access link is performed between the relay and theUE. Accordingly, the BS or the UE shown in FIG. 13 may be replaced withthe relay according to situation.

Referring to FIG. 13, a wireless communication system includes a BS 110and a UE 120. The BS 110 includes a processor 112, a memory 114, and aradio frequency (RF) unit 116. The processor 112 may be configured toperform the procedures and/or methods proposed in the present invention.The memory 114 is connected to the processor 112 and stores varioustypes of information related to operations of the processor 112. The RFunit 116 is connected to the processor 112 and transmits and/or receivesradio signals. The UE 120 includes a processor 122, a memory 124, and anRF unit 126. The processor 122 may be configured to perform the proposedprocedures and/or methods according to the present invention. The memory124 is connected to the processor 122 and stores various types ofinformation related to operations of the processor 122. The RF unit 126is connected to the processor 122 and transmits and/or receives radiosignals. The BS 110 and/or the UE 120 may include a single antenna ormultiple antennas.

The embodiments of the present invention described above arecombinations of elements and features of the present invention in apredetermined form. The elements or features may be considered selectiveunless otherwise mentioned. Each element or feature may be practicedwithout being combined with other elements or features. Further, anembodiment of the present invention may be constructed by combiningparts of the elements and/or features. Operation orders described inembodiments of the present invention may be rearranged. Someconstructions of any one embodiment may be included in anotherembodiment and may be replaced with corresponding constructions ofanother embodiment. It is obvious to those skilled in the art thatclaims that are not explicitly cited in each other in the appendedclaims may be presented in combination as an embodiment of the presentinvention or included as a new claim by subsequent amendment after theapplication is filed.

A specific operation described as being performed by the BS in thisdisclosure may be performed by an upper node of the BS in some cases.That is, it is apparent that, in a network comprised of a plurality ofnetwork nodes including the BS, various operations performed forcommunication with the UE can be performed by the BS or network nodesother than the BS. The term BS may be replaced with a fixed station, aNode B, an eNode B (eNB), an access point, etc.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to exemplaryembodiments of the present invention may be achieved by one or moreapplication specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, an embodiment of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. Software code may be stored in a memory unit and executedby a processor. The memory unit may be located at the interior orexterior of the processor and may transmit and receive data to and fromthe processor via various known means.

The memory unit may be located inside or outside the processor toexchange data with the processor by various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

While the above-described method of supporting a fallback operation in awireless communication system supporting usage change of a radioresource and the apparatus therefor have been described centering on anexample applied to a 3GPP LTE system, the present invention isapplicable to a variety of wireless communication systems in addition tothe 3GPP LTE system.

1. A method of reporting channel state information (CSI) by a userequipment (UE) in a wireless communication system supporting usagechange of a radio resource, the method comprising: receiving areconfiguration message for dynamically changing usage of the radioresource; measuring the CSI in a CSI reference resource durationcorresponding to the reconfiguration message; and reporting the CSI to abase station (BS), wherein the CSI reference resource duration includesa first CSI measurement resource set and a second CSI measurementresource set, the first CSI measurement resource set includes aplurality of first radio resources having fixed radio resource usage,and the second CSI measurement resource set includes a plurality ofsecond radio resources having reconfigurable radio resource usage. 2.The method according to claim 1, wherein the CSI is set to a predefinedvalue to indicate a fallback mode when the second CSI measurementresource set is invalid.
 3. The method according to claim 2, wherein theCSI is reported through a predefined uplink resource for the fallbackmode.
 4. The method according to claim 1, wherein, when the second CSImeasurement resource set is invalid, the CSI is set to CSI reportedprior to the CSI reference resource duration, both the first CSImeasurement resource set and the second CSI measurement resource setbeing valid.
 5. The method according to claim 1, wherein the CSIreference resource duration is defined such that only radio resourcesafter a subframe in which the reconfiguration message is transmitted arevalid.
 6. The method according to claim 1, wherein the CSI referenceresource duration is defined such that only radio resources presentafter a start subframe of a time window in which the reconfigurationmessage is transmitted are valid.
 7. The method according to claim 6,wherein the time window is defined according to a period at which thereconfiguration message is identically transmitted.
 8. The methodaccording to claim 1, wherein the CSI reference resource duration isdefined such that only radio resources present prior to 4 ms from asubframe for reporting the CSI are valid.
 9. The method according toclaim 1, wherein reporting of the CSI corresponds to aperiodic CSIreporting and the CSI reference resource duration is defined such thatonly radio resources present prior to a timing at which a triggeringmessage for reporting the CSI is received are valid.
 10. A userequipment (UE) for reporting channel state information (CSI) in awireless communication system supporting usage change of a radioresource, the UE comprising: a radio frequency unit; and a processor,wherein the processor is configured to receive a reconfiguration messagefor dynamically changing usage of the radio resource, measure the CSI ina CSI reference resource duration corresponding to the reconfigurationmessage, and report the CSI to a base station (BS), the CSI referenceresource duration includes a first CSI measurement resource set and asecond CSI measurement resource set, the first CSI measurement resourceset includes a plurality of first radio resources having fixed radioresource usage, and the second CSI measurement resource set includes aplurality of second radio resources having reconfigurable radio resourceusage.